Important words and concepts from Chapter 6, Black, 1999 (3/28/2003):

by Stephen T. Abedon (abedon.1@osu.edu) for Micro 509 at the Ohio State University

 

 

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Vocabulary words are found below

 

 

(1) Chapter Title: Growth and Culturing of Bacteria

(2) Microbial growth

(a)                    "Because individual cells grow larger only to divide into new individuals, microbial growth is defined not in terms of cell size but as the increase in the number of cells, which occurs by cell division."

(b)                    This emphasis has practical application since it is typically far easier to measure increases in cell number than it is to measure increases in cell size

(c)                    Furthermore, unless cell division is synchronized, cells will typically vary in size across an even homogeneous population, thus making measurement of cell size almost irrelevant as a means of measuring microbial growth

(d)                    Some general external links: [microbial growth (Google Search)] [microbial growth (with nice graphics) (David H. Demezas )] [Microbial Growth Dynamics (a book)] [microbial growth theory for biotreatment] [effects of random motility on microbial growth and competition in a flow reactor] [index]

(3) Binary fission

(a)                    The majority of bacteria reproduce by a mechanism termed binary fission

(b)                    Binary fission is much simpler than the mechanisms of cell division seen in eucaryotic cells

(c)                    See Figure 6.1, Binary fission

(d)                    [binary transverse fission] [binary fission (nice cartoon illustration)] [index]

(e)                    (if there are two fish in a lake, and one of them is dead, that’s called binary fishin’)

(f)                      [binary fission (Google Search)] [index]

(4) Tetrad

(a)                    Tetrads are a cell arrangement that is a consequence of binary fission not resulting in complete separation of cells, and that occurs in two planes, thus producing a square consisting of four cocci, one at each corner

(b)                    [tetrad and bacteria (Google Search)] [image, tetrad arrangement] [index]

(5) Sarcinae

(a)                    Sarcina are a cell arrangement that is a consequence of binary fission that does not result in complete separation of cells, and that occurs in three planes, thus producing cubes consisting of eight cocci, one coccus at each corner

(b)                    [sarcinae and bacteria (Google Search)] [image, sarcina arrangement] [index]

(6) Standard bacterial growth curve

(a)                    Bacteria added to fresh media typically go through four more-or-less distinct phases of growth

(i)                      Lag phase (A)

(ii)                    Log (logarithmic or exponential) phase (B)

(iii)                   Stationary phase (C)

(iv)                  Decline (death) phase (D)

(b)                   

(c)                    [standard bacterial growth curve, bacterial growth curve (Google Search)] [index]

(d)                    See Figure 6.3, A standard bacterial growth curve

(7) Lag phase

(a)                    Transfers of bacteria from one medium to another, where there exist chemical differences between the two media, typically results in a lag in cell division

(b)                    This lag in division is associated with a physiological adaptation to the new environment, by the cells, prior to their resumption of division

(c)                    That is, cells may increase in size during this time, but simply do not undergo binary fission

(d)                    [lag phase (Google Search)] [index]

(8) Log phase (logarithmic phase, exponential phase)

(a)                    Lag phase is followed by log phase during which binary fission occurs

(b)                    This phase of growth is called logarithmic or exponential because the rate of increase in cell number is a multiplicative function of cell number

(c)                    This can be seen in a graph of cell number versus time where cell numbers increase at ever increasing rates with time or generation; that is, the rate of increase is a function of absolute cell number such that the more cells present, the faster the population of cells increases in size (at least, during log phase)

(d)                    See Figure 6.4, Nonsynchronous growth

(e)                    When graphed on semi-log graph paper (Figure 6.3, i.e., log cell number versus time), log-phase growth produces a straight line

(f)                      [log phase, exponential phase, logarithmic phase (Google Search)] [illustration, exponential growth] [exponential growth rate (a student activity)] [index]

(9) Continuous culture (serial transfer)

(a)                    A means of keeping cultures in log phase can be accomplished either by employing a chemostat or via serial transfer

(b)                    A chemostat involves adding fresh medium to a culture, mixing, and then allowing an equal volume of culture to drain from the vessel; this is typically done continuously (i.e., a steady stream of fresh medium is added)

(c)                    Serial transfer means taking a volume of culture and diluting that volume into fresh media

(d)                    ["continuous culture" and bacteria, "serial transfer" and bacteria (Google Search)] [index]

(10) Generation time

(a)                    Generation time it takes a bacterial population to double in size (number) during log-phase growth

(b)                    Note that the time it takes for the population to double in size does not change with cell number (so long as cells remain in log phase)

(c)                    That is, with exponential growth, the absolute increase in cell number increases as cell number increases while the relative increase remains invariant

(d)                    Typically, generation times range from 20 minutes to 20 hours depending on the bacterial species/strain and the conditions during which log-phase growth is occurring

(e)                    ["generation time" and bacteria (Google Search)] [index]

(11) Stationary phase

(a)                    Stationary phase is a steady-state equilibrium where the rate of cell growth (division) is exactly balanced by the rate of cell death (i.e., increase in cell number due to cell divisions exactly balanced by a decrease in cell number due to death)

(b)                    Cell death (or, at least, lack of cell growth) occurs because of a loss of limiting nutrients (due to their incorporation into cells during log-phase growth) or a build-up of toxins (due to their release during log-phase growth, e.g., fermentative products)

(c)                    Note that the simplest conditions that will result in a stationary phase is when both the rate of cell increase and the rate of cell death together equal zero (i.e., cells neither die nor are born)

(d)                    [stationary phase (Google Search)] [index]

(12) Decline phase (death phase)

(a)                    Stationary phase, in a standard bacterial growth curve, is followed by a die-off of cells

(b)                    Cell death in bacteria cultures basically means that the cells are unable to resume division following their transfer to new environments

(c)                    Typically this die-off occurs exponentially, i.e., such that cell number graphed against time, using a semi-log scale for cell number, results in a straight line (i.e., see Figure 6.3)

(d)                    This death occurs because vegetative cells can survive exposure to harsh conditions (few nutrients or too-many toxins) for only so long

(e)                    ["decline phase" and bacteria, "death phase" and bacteria (Google Search)] [index]

 

Stop material covered this day; Start material below next day

 

(13) Solid medium

(a)                    Solid media contains agar, which is a compound that goes into water solution at temperatures approaching boiling, and then, once in solution, solidifies the medium at room (<40ºC) temperature

(b)                    Subsequent exposure to high temperature (i.e., boiling) will melt the medium

(c)                    Exposure to relatively low temperatures (i.e., >40ºC), however, will not melt the medium, thus allowing incubation of solid medium at various temperatures (compare to gelatin which liquefies at 37ºC)

(d)                    Once boiled, agar-containing medium will stay liquid at 45ºC

(e)                    This allows solid medium to be poured into various vessels at temperatures that will not kill most cells (nor melt vessels), followed by a solidification of the medium

(f)                     

(g)                    ["solid medium" and bacteria (Google Search)] [index]

(14) Colonies

(a)                    Colonies represent piles of cells descended, assuming pure culture technique and sufficiently few colonies on a single plate, from a single parent cell, all growing on or in a solid medium

(b)                   

(c)                    The four phases of bacterial growth can be observed within a single colony, with the edges displaying lag and log phases and the interior can display stationary and then decline phases

(d)                    Various colony morphologies (no need to memorize):

(e)                   

(f)                     

(g)                    [bacterial colony (Google Search)] [index]

(15) Pour plate

(a)                    The pour-plate method is employed for bacterial-cell enumeration and isolation

(b)                    In the pour-plate method of addition of cells to solid medium contained within a petri dish, cells are added to melted (but not too hot) solid medium

(c)                    The melted solid medium is then poured into a petri dish and allowed to harden

(d)                    Colonies appear both within, beneath, and on top of the agar

(e)                    See Figure 6.7, Calculation of the number of bacteria per milliliter of culture using serial dilution

(f)                      [pour plate (Google Search)] [index]

(16) Spread plate

(a)                    The spread plate method is employed for bacterial-cell enumeration and isolation

(b)                    In the spread-plate method of addition of cells to solid medium, a small volume of culture is dropped onto the surface of agar that has already hardened in a petri dish

(c)                    The volume is then spread around the agar surface

(d)                    Colonies will grow solely on the surface of the agar

(e)                    This technique is advantageous particularly when cells are sensitive to exposure to relatively high temperatures plus the method does not require a prior melting of the solid medium

(f)                     See Figure 6.7, Calculation of the number of bacteria per milliliter of culture using serial dilution

(g)                    [spread plate (Google Search)] [index]

(17) Standard plate count (heterotrophic plate count)

(a)                    When bacteria are placed on a solid medium, ideally each colony is founded by only a single bacterial cell (obviously, given clumping and various cell arrangements, this ideal is not always met)

(b)                    Thus, addition of a known quantity of bacterial cells to a solid medium should produce the same number of colonies

(c)                    This result can be employed backward so that the number of colonies grown on solid medium can be used to estimate the number of individual bacteria that were added to the solid medium

(d)                    This number, in turn, may be employed to estimate the concentration of bacteria present in a culture

(e)                    [standard plate count, heterotrophic plate count (Google Search)] [index]

(18) Colony-forming unit (CFU)

(a)                    Whether a single cell or a clump of cells or whatever, what grows into an isolated colony is termed a colony-forming unit

(b)                    When doing standard plate counts, what is being estimated are numbers of colony-forming units

(c)                    The number of colonies that may be counted per petri dish (and therefore the number CFUs that may be enumerated) is limited by statistics (at the low end) and space on the dish (at the upper end) to between 30 and 300 colonies/CFUs per plate

(d)                    See Figure 6.8, Counting colonies

(e)                    [colony-forming unit (Google Search)] [index]

(19) Serial dilution

(a)                    For a given agar surface, there are only so many colonies that may be present before it becomes impossible to accurately count the number of colonies present

(b)                    This number serves as a limit on the concentration of bacteria in cultures that may be enumerated using the standard plate-count technique

(c)                    How to get around this limitation? This may be achieved by diluting cultures before enumerating them

(d)                    By keeping track numerically of the degree of diluting employed, the concentration of bacteria in the pre-diluted culture may be estimated

(e)                    Due to limitations in the size of the volumes that may be conveniently handled (i.e., both very large volumes and very small volumes are difficult to handle), relatively large dilutions are typically handled serially

(f)                      For example, a 10-fold dilution followed by a second 10-fold dilution (i.e., 1 ml from a parent culture diluted to 9 ml diluent followed by mixing followed by 1 ml from the diluted culture diluted to an additional 9 ml diluent followed by mixing) gives a total of a 100-fold dilution

(g)                   

(h)                    See Figure 6.6, Serial dilution

(i)                      See Figure 6.7, Calculation of the number of bacteria per milliliter of culture using serial dilution

(j)                      [serial dilution (Google Search)] [index]

(20) Direct microscopic counts

(a)                    A more direct means of enumerating bacteria is done by viewing them through a microscope

(b)                    This method's limitations are that only relatively high concentrations of bacteria may be enumerated and the method cannot distinguish living from dead bacteria

(c)                    See Figure 6.9, The Petroff-Hausser counting chamber

(d)                    [direct microscopic count (Google Search)] [index]

(21) Most probable number method (MPN method)

(a)                    Organisms that cannot grow on solid media can still be enumerated using the most probable number method

(b)                    Once again, cultures are diluted, here into a suitable broth medium

(c)                    "The more tubes that show growth, especially at greater dilutions, the more organisms were present in the sample."

(d)                    Particularly, at some greater dilution there will be on average no organisms added per tube of broth, while at lesser dilutions there will be organisms in every tube; the middle dilution at which the transition is made from all tubes inoculated with organism to few or none represents approximately the inverse of the concentration of organisms in the original culture

(e)                    See Figure 6.10, A most probable number (MPN) test [note: need to make transparency of MPN table in appendix A]

(f)                      [most probable number method, most probable number test (Google Search)] [index]

(22) Turbidity

(a)                    The degree of turbidity (cloudiness) exhibited by a broth culture gives an indication of the number of organisms present

(b)                    Degree of turbidity varies with organisms, conditions, and phase of growth so use of turbidity as a form of enumeration requires previous standardization

(c)                    As with direct microscopic counts, use of turbidity is limited to relatively high cell concentrations

(d)                    [culture turbidity (Google Search)] [microbial growth monitors] [index]

(23) Biochemical determinations

(a)                    The rate of use of substrates or liberation of metabolic products also can be employed as methods of enumeration, though just as with turbidity, prior standardization is necessary

(24) Dry weight

(a)                    A time-consuming method of culture-mass determination involves drying cells (removing water) and then weighing them

(b)                    ["dry weight" and bacteria (Google Search)] [index]

(25) Factors affecting bacterial growth

(a)                    "The kinds of organisms found in a given environment and the rates at which they grow can be influenced by a variety of factors, both physical and biochemical. Physical factors include pH, temperature, oxygen concentration, moisture, hydrostatic pressure, osmotic pressure, and radiation. Nutritional (biochemical) factors include availability of carbon, nitrogen, sulfur, phosphorus, trace elements, and, in some cases, vitamins."

(26) pH

(a)                    Recall that the pH scale measures hydrogen ion (H+) concentration and that low pHs correspond with high concentrations of hydrogen ion, neutral pH with equal numbers of hydrogen and hydroxyl ions (OH-), and high pHs correspond to low concentrations of hydrogen ion

(b)                    [pH (MicroDude)] [index]

(27) Optimum pH

(a)                    Optimum pH is that pH at which a given organism grows best

(b)                    The range over which most organisms can grow tends to vary over no more than a single pH unit in either direction (e.g., from pH 6 to pH 8 for an organism whose pH optimum is pH 7)

(c)                    ["optimum pH" and bacteria (Google Search)] [index]

(28) Acidophiles

(a)                    Organisms whose optimum pH is relatively to highly acidic

(b)                    [acidophile (Google Search)] [index]

(29) Neutrophiles

(a)                    Organisms whose optimum pH ranges about pH 7, plus or minus approximately 1.5 pH units

(b)                    [neutrophile and bacteria (Google Search)] [index]

(30) Alkaphiles

(a)                    Organisms whose optimum pH is relatively to highly basic

(b)                    [alkaphile (very few hits) (Google Search)] [index]

(31) Optimum temperature

(a)                    Optimum temperature is the temperature at which an organism grows best

(b)                    See Figure 6.14, Growth rates of psychrophilic, mesophilic, and thermophilic bacteria

(c)                    Typically the range in temperature over which a bacterium can grow is about 30ºC

(d)                    ["optimum temperature" and bacteria (Google Search)] [index]

(32) Psychrophile

(a)                    Cold-adapted organisms are called psychrophiles

(b)                    The cut-off temperature for a psychrophile is a 20ºC or colder temperature optimum

(c)                    Psychrophiles may additionally be termed obligate or facultative with obligate psychrophiles unable to grow above 20ºC, but facultative psychrophiles are able to

(d)                    [psychrophile (Google Search)] [index]

(33) Mesophile

(a)                    Organisms whose optimum growth temperatures is found between 20ºC to 40ºC are termed mesophiles

(b)                    Human pathogens, which must be able to grow at the approximately 37ºC body temperature, are mesophiles

(c)                    [mesophile (Google Search)] [index]

(34) Thermoduric

(a)                    Mesophilic organisms that can endure brief exposures to relatively high temperatures are termed thermoduric

(b)                    These are one category of the organisms that survive following inadequate heating of foods and may thereby contribute to the spoilage of foods that have been heated (e.g., Pasteurization) to kill microorganisms

(c)                    [thermoduric (Google Search)] [index]

(35) Thermophile

(a)                    High-temperature-adapted organisms are called thermophiles

(b)                    [thermophile (Google Search)] [index]

(36) Oxygen requirements

(a)                    Organisms differ in their requirements of molecular oxygen (i.e., O2) as well as other atmospheric gasses (e.g., carbon dioxide)

(b)                    Categories of oxygen requirements include:

(i)                      Obligate aerobes

(ii)                    Obligate anaerobes

(iii)                   Microaerophiles

(iv)                  Facultative anaerobes

(v)                    Aerotolerant anaerobes

(vi)                  Strict anaerobes

(c)                    See Figure 6.15, Patterns of oxygen use

(d)                    ["oxygen requirements" and bacteria (Google Search)] [index]

(37) Obligate aerobe

(a)                    Organisms that are unable to generate ATP via fermentation are termed obligate aerobes

(b)                    This term is somewhat misleading because some of these organisms can still grow in the absence of molecular oxygen by employing alternative final electron acceptors to their electron transport systems

(c)                    The bottom line, then, for an obligate aerobe is a dependence on an electron transport system for their generation of ATP as well as a tolerance for atmospheric oxygen (which otherwise can serve as a poison)

(d)                    [obligate aerobe (Google Search)] [index]

(38) Obligate anaerobe

(a)                    Organisms that are unable to detoxify atmospheric oxygen are termed obligate anaerobes because they cannot grow (nor, often, even survive) in the presence of oxygen

(b)                    Obviously, obligate anaerobes must possess means for ATP generation that do not require molecular oxygen, e.g., fermentation pathways

(c)                    [obligate anaerobe (Google Search)] [index]

(39) Microaerophile

(a)                    These are organisms that grow best when small amounts of oxygen are present

(b)                    That is, less (typically much less) than atmospheric concentrations, but more than those concentrations tolerable by obligate anaerobes

(c)                    [microaerophile (Google Search)] [index]

(40) Facultative anaerobe

(a)                    Facultative anaerobes can generate ATP by either aerobic or anaerobic means and have the means to detoxify oxygen

(b)                    These organisms tend to exist in environments in which oxygen concentrations are uncertain, and serve as the oxygen scavengers in environments displaying relatively low oxygen concentrations

(c)                    For example, the lumen of the large intestine is mostly anaerobic because (i) the body does not actively oxygenate the lumen of the large intestine and (ii) oxygen scavengers such as Escherichia coli remove what oxygen manages to leak into this environment

(d)                    Facultative anaerobes tend to grow better/faster when O2 is present

(e)                    [facultative anaerobe (Google Search)] [index]

(41) Aerotolerant anaerobe

(a)                    These are organisms that are unable to utilize molecular oxygen in their ATP generation but otherwise possess the means to detoxify oxygen

(b)                    This allows, if nothing else, the safe passage of these organisms through aerobic environments

(c)                    Lactobacillus spp. for example generate their ATPs by fermentation regardless of the oxygen concentrations of the environment

(d)                    [aerotolerant anaerobe (Google Search)] [index]

(42) Strict anaerobe

(a)                    A strict anaerobe is unable to replicate, and may even die given the presence of oxygen

(b)                    This inability or fragility results from a lack of enzymes necessary to detoxify molecular oxygen

(c)                    [strict anaerobe (Google Search)] [index]

 

 

Genera

O2 Requirements

 

Bacillus

 

X

Bacteroides

 

X

Clostridium

 

X

Enterobacter

 

X

Escherichia

 

X

Gardnerella

 

X

Haemophilus

 

X

Klebsiella

 

X

Legionella

 

X

Mycobacterium

 

X

Pasteurella

 

X

Proteus

 

X

Pseudomonas

 

X

Salmonella

 

X

Serratia

 

X

Shigella

 

X

Yersinia

 

X

Corynebacterium

 

X

Moraxella

 

X

Vibrio

 

X

Bordetella

 

X

 

 

 

Chlamydia

 

X

Neisseria

 

X

Staphylococcus

 

X

Streptococcus

 

X

 

 

 

Streptomyces

 

X

Mycoplasma

 

X

Rickettsia

 

X

 

 

 

Campylobacter

 

X

Helicobacter

 

X

Borrelia

 

X

Treponema

 

X

Sample question: Full credit for 13 entered

correctly (with credit off for incorrect entries):

 

Genera

O2 Requirements

Bacillus

 

Bacteroides

 

Clostridium

 

Enterobacter

 

Escherichia

 

Gardnerella

 

Haemophilus

 

Klebsiella

 

Legionella

 

Mycobacterium

 

Pasteurella

 

Proteus

 

Pseudomonas

 

Salmonella

 

Serratia

 

Shigella

 

Yersinia

 

Corynebacterium

 

Moraxella

 

Vibrio

 

Bordetella

 

Chlamydia

 

Neisseria

 

Staphylococcus

 

Streptococcus

 

Streptomyces

 

Mycoplasma

 

Rickettsia

 

Campylobacter

 

Helicobacter

 

Borrelia

 

Treponema

 

 

 

(43) Capnophiles

(a)                    These are organisms whose optimum growth requires relatively high concentrations of carbon dioxide

(b)                    [capnophiles (Google Search)] [index]

(44) Osmotic pressure

(a)                    The concentration of dissolved substances in the environment can impact on the growth and survival of cells

(b)                    [osmosis (MicroDude)] [index]

(45) Plasmolysis

(a)                    Environments containing large concentrations of dissolved substances draw water out of cells, causing a shrinkage of the cytoplasm volume, a phenomenon termed plasmolysis

(b)                    Plasmolysis interferes with growth and this is why highly osmotic environments prevent bacterial growth (e.g., brine, the high sugar concentrations in jellies and jams, salting of meats)

(c)                    [plasmolysis and bacteria (Google Search)] [index]

(46) Halophiles

(a)                    Organisms that require high concentrations of dissolved salts to grow are termed halophiles

(b)                    Depending on organism, the salt concentrations required range from those of sea water on up to those of brine

(c)                    [halophiles (Google Search)] [index]

(47) Nutritional factors

(a)                    All microorganisms require the following nutrients to grow, repair themselves, and to replicate:

(i)                      Carbon

(ii)                    Nitrogen

(iii)                   Sulfur

(iv)                  Phosphorus

(v)                    Various trace elements

(b)                    In addition, some microorganisms require various vitamins as well as additional organic factors (e.g., specific amino acids)

(c)                    "Although we are concerned with ways microorganisms satisfy their own nutritional needs, we can note that in satisfying such needs, they also help recycle elements in the environment."

(i)                      That is, microorganisms are typically able to obtain nutrients from sources that macroorganisms are not

(48) Fastidious

(a)                    Microorganisms whose nutritional needs are unusually complex are termed fastidious

(b)                    [fastidious and bacteria (Google Search)] [index]

(49) Nitrogen sources

(a)                    Nitrogen may be obtained from inorganic sources (e.g., nitrate ions, NO3-, or ammonium ion, NH4+) or from organic sources (i.e., amino acids or nucleotides)

(b)                    In contrast, organisms such as ourselves obtain nitrogen solely from organic sources

(c)                    Many microorganisms (e.g., E. coli) can satisfy all of their nitrogen needs from inorganic sources

(d)                    Fastidious microorganisms may require one or more amino acid in their growth medium because they are unable to synthesize that amino acid (just as we have various essential amino acids that we must obtain from our diet because we are unable to synthesize them ourselves)

(e)                    [nitrogen and "culture medium" and bacteria (Google Search)] [index]

(50) Sulfur

(a)                    Like nitrogen, sulfur may be obtained from organic sources (sulfur-containing amino acids) or from inorganic sources

(b)                    [sulfur and "culture medium" and bacteria (Google Search)] [index]

(51) Phosphorous

(a)                    Unlike nitrogen and sulfur, phosphorous is typically obtained by microorganisms in its inorganic form, i.e., the phosphate ion (PO43-).

(b)                    [phosphorus and "culture medium" and bacteria (Google Search)] [index]

(52) Trace elements

(a)                    Trace elements are required in relatively small quantities

(b)                    Typically these elements are employed as enzyme cofactors, e.g., metals to which enzymes must complex with in order to function properly

(c)                    ["trace elements" and "culture medium" and bacteria (Google Search)] [index]

(53) Vitamins

(a)                    Vitamins are essentially organic equivalents of trace elements, i.e., organic molecules required in relatively small amounts which various enzymes must complex with in order to function properly

(b)                    While many microorganism can synthesize vitamins, others cannot and an inability to synthesize vitamins contributes to an organism's fastidiousness since vitamins consequently must be supplied in the organism's growth medium

(c)                    [vitamins and "culture medium" and bacteria (Google Search)] [index]

(54) Exoenzymes

(a)                    Microorganisms employ enzymes as well as transport proteins to bring substances into their cytoplasm to either be broken down in catabolic reactions or used as building blocks to produce more complex substances via anabolic pathways

(b)                    If an organism possesses sufficient kinds of enzymes, they can break down or build up just about anything, though no organism possesses all possible enzymes so consequently no organism is capable of breaking down nor building up everything

(c)                    In addition to enzymes found within their cells, many bacteria (as well as fungi and ourselves) produce enzymes that are secreted from cells into the surrounding medium

(d)                    These enzymes typically are employed to break down nutrients found outside of cells (extracellularly) so that the breakdown products may be taken up into the cell and used

(e)                    Many of these enzymes are harmful and represent exotoxins produced by disease-causing microorganisms, especially Gram-positive bacteria

(f)                      [exoenzyme (Google Search)] [index]

(55) Periplasmic enzymes

(a)                    To some extent equivalent to the exoenzymes used by Gram-positive bacteria, Gram-negative bacteria employ enzymes secreted into their periplasm to break down large molecules before those molecules are brought across the plasma membrane and into the cytoplasm

(b)                    [periplasmic enzymes (Google Search)] [index]

(56) Culture medium

(a)                    To successfully grow microorganisms, one must employ a culture medium that contains all of the nutrients required by an organism (as well as conditions that meet an organism's physical requirements)

(b)                    Media may be differentiated in various ways

(c)                    [culture medium (Google Search)] [index]

(57) Broth versus solid media

(a)                    Broth media is liquid while solid media typically has agar added as a solidifying agent

(b)                    Semi-solid media also exists that contains insufficient quantities of agar to fully solidify the media

(58) Synthetic medium

(a)                    A synthetic medium is prepared in the laboratory from reasonably well-defined ingredients

(b)                    By contrast, a not synthetic medium could be something like soil or sewage or ocean mud, i.e., something obtained directly from the environment

(c)                    [synthetic medium (Google Search)] [index]

(59) Defined synthetic medium

(a)                    A defined synthetic medium is produced only from well-defined, relatively pure ingredients

(b)                    See Table 6.2, A defined synthetic medium for growing Proteus vulgaris

(c)                    See Table 6.3, A defined synthetic medium for growing the fastidious bacterium Leuconostoc mesenteroides

(d)                    [defined synthetic medium (Google Search)] [index]

(60) Complex media (chemically undefined media)

(a)                    A second approach to producing a synthetic medium is to employ ingredients that are not well-defined nor pure

(b)                    Such ingredients additionally may vary from batch to batch

(c)                    For example, complex media may contain extracts from animals (e.g., beef, hearts, milk, etc.), plants (e.g., soy beans), or microorganisms (e.g., yeast)

(d)                    Complex media may additionally include very complex ingredients such as blood

(e)                    ["complex media" and bacteria (Google Search)] [index]

(61) Selective media

(a)                    Selective media acts to inhibit the growth of certain kinds of microorganisms while allowing the growth of other

(b)                    [selective media (Google Search)] [index]

(62) Differential media

(a)                    Differential media contains ingredients that allow different microorganisms to look reproducibly different

(b)                    Consequently, one may determine whether a given organism is present in a culture on the basis of colony morphology alone

(c)                    Confusingly, many media employed in microbiological laboratories are both differential and selective

(d)                    That is, many media both inhibit the growth of certain microorganisms while making those organisms that it allows to grow produce easily differentiated colony morphologies

(e)                    See Table 6.5, Selected examples of diagnostic media

(f)                      [differential media (Google Search)] [index]

(63) Vocabulary [index]

(a)                    Acidophiles

(b)                    Aerotolerant anaerobe

(c)                    Alkaphiles

(d)                    Binary fission

(e)                    Biochemical determinations

(f)                      Broth versus solid media

(g)                    Capnophiles

(h)                    CFU

(i)                      Chemically undefined media

(j)                      Colonies

(k)                    Colony-forming unit

(l)                      Complex media

(m)                  Continuous culture

(n)                    Culture medium

(o)                    Death phase

(p)                    Decline phase

(q)                    Defined synthetic medium

(r)                     Differential media

(s)                     Direct microscopic counts

(t)                      Dry weight

(u)                    Exoenzymes

(v)                    Exponential phase

(w)                  Factors affecting bacterial growth

(x)                    Facultative anaerobe

(y)                    Fastidious

(z)                     Generation time

(aa)                 Halophiles

(bb)                Lag phase

(cc)                 Log phase

(dd)                Logarithmic phase

(ee)                 Mesophile

(ff)                    Microaerophile

(gg)                 Microbial growth

(hh)                 Most probable number (MPN) method

(ii)                     MPN

(jj)                    Neutrophiles

(kk)                Nitrogen sources

(ll)                     Nutritional factors

(mm)             Obligate aerobe

(nn)                 Obligate anaerobe

(oo)                Optimum pH

(pp)                Optimum temperature

(qq)                Osmotic pressure

(rr)                   Oxygen requirements

(ss)                  Periplasmic enzymes

(tt)                    pH

(uu)                 Phosphorous

(vv)                 Plasmolysis

(ww)             Pour plate

(xx)                 Psychrophile

(yy)                 Sarcinae

(zz)                  Selective media

(aaa)             Serial dilution

(bbb)            Serial transfer

(ccc)             Solid medium

(ddd)            Spread plate

(eee)             Standard bacterial growth curve

(fff)                  Standard plate count

(ggg)             Stationary phase

(hhh)             Strict anaerobe

(iii)                   Sulfur

(jjj)                  Synthetic medium

(kkk)            Tetrad

(lll)                   Thermoduric

(mmm)       Thermophile

(nnn)             Trace elements

(ooo)            Turbidity

(ppp)            Vitamins