Important words and concepts from Chapter 4, Black, 2002 (3/28/2003):

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

 

 

Course-external links are in brackets

Click [index] to access site index

Click here to access text’s website

Vocabulary words are found below

 

 

(1) Chapter Title: Characteristics of Prokaryotic and Eukaryotic Cells

(a)                    Found at this site are additional pages of possibly related interest including: [a tour of the cell (MicroDude)] [membrane structure and function (MicroDude)] [supplemental cell biology lectures (MicroDude)]

 

PROKARYOTES (them) vs. EUKARYOTES (us)

 

(2) Classification of cells

(a)                    Across all types of organisms, cells may be classified into two fundamental morphological types: Prokaryotes and Eukaryotes

(b)                    A given organism will possess cells of one of these types, but not both (though there is an exception to this rule, endosymbiosis, that we will discuss)

(c)                    [cell theory (Google Search)] [index]

(3) Prokaryotes

(a)                    Organisms classified as prokaryotes have a number of defining features that differentiate their cell type from the eukaryote cell type

(i)                      Prokaryotic cells lack a nucleus

(ii)                    Prokaryotic cells tend to lack other membrane-bound organelles (the nucleus, itself, also represents a membrane-bound organelle)

(iii)                   [more-complete comparison of prokaryotic and eukaryotic cell features (Doc Kaiser’s Microbiology Web Page)] [index]

(b)                    We will focus in this lecture on the cellular anatomy of prokaryotic cells since the majority of this course will deal with bacteria, which are prokaryotes

(c)                    We will additionally call attention to the existence of prokaryote-like organelles that are found in most eukaryotic cells

(d)                    Finally, we will consider how membranes function

(e)                    Prokaryotes typically, though not exclusively, exist as unicellular organisms

(f)                      [prokaryotic cells (Google Search)] [a prokaryotic cell] [composition and functions of bacterial structures] [index]

(4) Eukaryotes

(a)                    Organisms that possess the eukaryotic cell type include

(i)                      Animals

(ii)                    Plants

(iii)                   Fungi

(iv)                  Algae

(v)                    Protozoa

(b)                    See Table 4.1, Similarities and differences between prokaryotic and eukaryotic cells

(c)                    [eukaryotic cells (Google Search)] [a eukaryotic cell] [index]

(5) Domains

(a)                    An even more fundamental means of distinguishing organisms than into prokaryotes and eukaryotes is their categorization into domains (supplanting “kingdoms” the domain is now the highest of taxonomic categories)

(b)                    There exist three domains

(i)                      Archaea (archaeobacteria) which are prokaryotes

(ii)                    Bacteria (eubacteria) which are prokaryotes

(iii)                   Eukarya which are eukaryotes

(c)                    Note that Table 4.1 compares and contrasts Bacteria with Eukarya, leaving Archaea out; this is a typical emphasis within microbiology, and among microbiologists, and we won’t fight it

(d)                    [three-domain system (Google Search)] [universal tree (MicroDude)] [index]

(6) Size of prokaryotes

(a)                    Prokaryotic cells are typically much smaller than eukaryotic cells

(b)                    This gives prokaryotic cells a large surface-to-volume ratio which makes up for their comparative morphological simplicity

(c)                    Eukaryotic cells are larger and possess numerous internal membranes that help to make up for their small plasma-membrane-to-cytoplasmic-volume ratio

(d)                    Mitochondria and chloroplasts, found as organelles in eukaryotic cells, on the other hand, approximate the size of prokaryotic cells

(e)                    A large surface-to-volume ratio is advantageous for an organism that acquires nutrients by absorption since there is comparatively more absorption surface (the plasma membrane) and comparatively less of a requirement for absorbed nutrients (the cytoplasmic volume)

(f)                      Thus, the small size as well as simple morphology of bacteria is well suited to their absorption-of-nutrients-from-the-environment ecological niche

(g)                    [size of prokaryotes (Google Search)] [index]

 

BACTERIA MORPHOLOGY

 

(7) Bacterial shapes (coccus, bacillus, coccobacillus, spirillum, spirochete)

(a)                    Consistent with the simple morphology and small size of bacteria, their basic shapes also tend to be relatively simple

(b)                    Bacterial shapes may be typically divided into the following categories

(i)                      Coccus (cocci) = spherical [arrangements of cocci]

(ii)                    Bacillus (bacilli) = rod-shaped [arrangements of bacilli]

(iii)                   Coccobacillus = intermediate to coccus and bacillus

(iv)                  Spirillum = wavy spiral-shaped [shape of spirillium]

(v)                    Spirochete = corkscrew spiral-shaped

(vi)                  Etc. = square-shaped, star-shaped, filamentous, etc.

(c)                    Bacterial shapes, depending on the organism, can change subtly when cells are growing or existing under different conditions, e.g., a shortening of rods as nutrient concentrations are used up and therefore as growth rates decline; this will be especially obvious as you attempt to classify the shape of such things as stationary-phase Escherichia coli

(d)                    See Figure 4.1, The most common bacterial shapes

(e)                    [bacterial shapes (Google Search)] [index]

(8) Pleomorphic

(a)                    Some bacteria do not display a constant shape even during growth in an otherwise unchanging, homogeneous environment

(b)                    Such bacteria are termed pleomorphic to indicate that they do not possess a relatively constant standard shape even under relatively constant, standard conditions

(9) Bacterial cell arrangements (diplo-, strepto-, tetrad, sarcina, staphylo-)

(a)                    While some bacteria cells separate completely following division, others remain attached

(b)                    Attached cells typically take on a characteristic arrangement that differs depending on the bacteria, the bacterial shape, and the planes in which cell division occurs [arrangements of cocci] [arrangements of bacilli]

(c)                    Typical bacterial arrangements include:

(i)                      Diplo- = cells remain attached in pairs (e.g., diplococcus) [image, diplococcus]

(ii)                    Strepto- = cells remain attached in chains (e.g., streptococcus) [image, streptococcus] [image, streptobacillus]

(iii)                   Tetrads = cells arranged in squares (note two planes of division) [image, tetrad arrangement]

(iv)                  Sarcinae = cells arranged in cubes (note three planes of division) [image, sarcina arrangement]

(v)                    Staphylo- = random planes of division resulting in sheets and clumps [image, staphylococcus] [image, Staphylococcus aureus]

(d)                    Bacilli typically divide within only a single plane of division so are limited to diplo- or strepto-forms [arrangements of bacilli]

(e)                    See Figure 4.2, Arrangements of bacteria

(f)                       

(g)                    ["cellular arrangements" and bacteria (Google Search)] [sizes, shapes, and arrangements of bacteria (Biol 230 MicrobiologyGary E. Kaiser)] [index]

 

 

Genera

Shape

 

Bacillus

bacillus

X¯

Bacteroides

bacillus

X¯

Clostridium

bacillus

X¯

Enterobacter

bacillus

X¯

Escherichia

bacillus

X¯

Gardnerella

bacillus

X¯

Haemophilus

bacillus

X¯

Klebsiella

bacillus

X¯

Legionella

bacillus

X¯

Mycobacterium

bacillus

X¯

Pasteurella

bacillus

X¯

Proteus

bacillus

X¯

Pseudomonas

bacillus

X¯

Salmonella

bacillus

X¯

Serratia

bacillus

X¯

Shigella

bacillus

X¯

Yersinia

bacillus

X¯

Corynebacterium

bacillus (pleomorphic)

X¯

Moraxella

bacillus (short)

X¯

Vibrio

bacillus (with bend)

X¯

Bordetella

coccobacillus

X¯

 

 

 

Chlamydia

coccus

X¯

Neisseria

coccus (diplococcus)

X¯

Staphylococcus

coccus (staphylococcus)

X¯

Streptococcus

coccus (streptococcus)

X¯

 

 

 

Streptomyces

filamentous

X¯

Mycoplasma

pleomorphic

X¯

Rickettsia

pleomorphic

X¯

 

 

 

Campylobacter

spirillum (helical)

X¯

Helicobacter

spirillum (helical)

X¯

Borrelia

spirochete

X¯

Treponema

spirochete

X¯

Sample question: Full credit for 13 entered

correctly (with credit off for incorrect entries):

 

Genera

Shape

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

 

 

BACTERIA ANATOMY

 

(10) Bacterial cellular anatomy

(a)                    For the sake of organization, bacterial cellular anatomy may be categorized into

(i)                      Those things found associated with the cell envelope

·        E.g., the plasma membrane, the cell wall, etc.

(ii)                    Those things found internal to the cell envelope

·        E.g., cytoplasm, ribosomes, nuclear regions, etc.

(iii)                   Those things found external to the cell envelope

·        E.g., capsules, flagella, pili, glycocalyx, etc.

(b)                    See Figure 4.3, A typical prokaryotic cell

(11) Cell wall

(a)                    The cell wall of a bacteria

(i)                      Is semirigid

(ii)                    Is found externally to the plasma membrane

(iii)                   Is responsible for maintaining the cell shape

(iv)                  Is responsible for protecting bacteria against osmotic lysis

(v)                    Consists of peptidoglycan, a.k.a., murein

(vi)                  Consists, in Gram-positive bacteria, additionally of teichoic acid

(b)                    Though most bacteria possess cell walls, not all do

(c)                    [bacterial cell wall (Google Search)] [cell wall anatomy] [index]

(12) Gram-negative cell wall

(a)                    The Gram-negative bacteria cell wall differs from the cell wall of Gram-positive bacteria in terms of

(i)                      The structure of the cell wall itself

(ii)                    The covering of the cell wall by an outer membrane

(iii)                   The existence of a distinct periplasm located between the outer membrane and the inner membrane

(b)                    [gram-negative cell wall (Google Search)] [structure of a Gram-negative cell wall] [index]

(13) Outer membrane

(a)                    The outer membrane is a feature of Gram-negative bacteria but not Gram-positive bacteria

(b)                    The outer membrane is found externally to the cell wall

(c)                    The outer membrane helps protect the cell wall and plasma membrane from environmental poisons

(d)                    The outer membrane additionally contains (i.e., surrounds) the periplasmic space

(e)                    See Figure 4.6b, The bacterial cell wall

(14) Inner membrane

(a)                    Inner membrane is another name for the Gram-negative plasma membrane

(b)                    [bacterial inner membrane (Google Search)] [enzymes of the inner membrane] [index]

(15) Lipopolysaccharide (LPS, endotoxin)

(a)                    A component of the outer-leaflet of the outer membrane of Gram-negative bacteria is LPS

(b)                    LPS consists of polysaccharide and Lipid A (the latter anchors the LPS into the outer membrane)

(c)                    Another name for Lipid A is endotoxin

(d)                    (“The major cause of death for patients with cystic fibrosis is the massive chronic infections with Pseudomonas aeruginosa that they acquire… Bacteria adapt to the particular environment of the patients’ lungs by synthesizing lipopolysaccharides with a specific structure. This modification in lipid A is associated with an increased inflammatory response and resistance to antimicrobial agents.” 1999, Science 286:1441-1443)

(e)                    [lipopolysaccharide and "outer membrane", LPS and "outer membrane", endotoxin and "outer membrane" (Google Search)] [index]

(16) Periplasmic space (periplasm)

(a)                    The periplasm is the volume between the inner and outer membranes

(b)                    Gram-negative bacteria digest nutrients in the periplasm prior to the transport of the nutrients into the cytoplasm

(c)                    (Gram-positive bacteria, by contrast, function more like fungi, employing exoenzymes that act beyond the cell to digest nutrients into forms that may then be taken up by the cell)

(d)                    In addition to breaking down nutrients, the periplasm additionally serves as a region in which potentially harmful substances are broken down (i.e., destroyed)

(e)                    See Figure 4.6b, The bacterial cell wall

(f)                      [periplasmic space, periplasmic space (Google Search)] [index]

(17) Endosymbiotic theory

(a)                    Note that you are likely already somewhat familiar with Gram-negative-bacterial structures (e.g., inner membrane, outer membrane, periplasmic space) since these structures are equivalently found in mitochondria and chloroplasts

(b)                    This is because mitochondria and chloroplasts are, in fact, Gram-negative bacteria

(c)                    Their similarity to Gram-negative bacteria continues further, including the existence in these eukaryote organelles of a nucleoid (nuclear regions) and Gram-negative-bacteria-like ribosomes

(d)                    See Figure 4.21, Mitochondria

(e)                    [periplasm and bacteria (Google Search)] [index]

(18) Gram-positive cell wall

(a)                    The Gram-positive cell wall differs from the Gram-negative cell wall in at least three ways

(i)                      It is considerably thicker than the Gram-negative cell wall

(ii)                    It contains teichoic acid

(iii)                   It is directly exposed to the extracellular environment (or, at least, is not covered by an outer membrane)

(b)                    The thickness of the cell wall allows the retention of the Gram stain thus accounting for the Gram-positive staining of these bacteria

(i)                      See Figure 4.6a, The bacterial cell wall

(c)                    [gram-positive cell wall (Google Search)] [index]

(19) Protoplast

(a)                    A Gram-positive cell that is treated with lysozyme (a peptidoglycan-digesting enzyme) within an isotonic environment (as we’ll define later) becomes spherical and is called a protoplast

(b)                    [note that there seems to be an amazing lack of information on bacteria protoplasts on the web; please let me know of any sites you know of on this subject]

(c)                    [protoplast and bacteria (Google Search)] [note that plant cells that  have had their cell walls removed are also called protoplasts] [index]

(20) Spheroplast

(a)                    Unlike Gram-positive bacteria, the digestion of a Gram-negative bacterium with lysozyme does not result in a complete removal of the outer membrane and these cells are termed spheroplasts rather than protoplasts

(b)                    [spheroplast and bacteria (Google Search)] [yeasts may also be spheroplasted] [Mycobacterium paratuberculosis may be found in either a bacillary or spheroplast form] [antibiotic-treated Borrelia burgdorferi can take on a pleomorphic, not replicating spheroplast-L-form variant] [index]

 

Genera

Stains

 

Mycobacterium

Acid fast

X¯

Bacteroides

Gram-negative

X¯

Bordetella

Gram-negative

X¯

Borrelia

Gram-negative

X¯

Campylobacter

Gram-negative

X¯

Chlamydia

Gram-negative

X¯

Enterobacter

Gram-negative

X¯

Escherichia

Gram-negative

X¯

Gardnerella

Gram-negative

X¯

Haemophilus

Gram-negative

X¯

Helicobacter

Gram-negative

X¯

Klebsiella

Gram-negative

X¯

Legionella

Gram-negative

X¯

Moraxella

Gram-negative

X¯

Mycoplasma

Gram-negative

X¯

Neisseria

Gram-negative

X¯

Pasteurella

Gram-negative

X¯

Proteus

Gram-negative

X¯

Pseudomonas

Gram-negative

X¯

Rickettsia

Gram-negative

X¯

Salmonella

Gram-negative

X¯

Serratia

Gram-negative

X¯

Shigella

Gram-negative

X¯

Treponema

Gram-negative

X¯

Vibrio

Gram-negative

X¯

Yersinia

Gram-negative

X¯

 

 

 

Bacillus

Gram-positive

X¯

Clostridium

Gram-positive

X¯

Corynebacterium

Gram-positive

X¯

Staphylococcus

Gram-positive

X¯

Streptococcus

Gram-positive

X¯

Streptomyces

Gram-positive

X¯

 

Sample question: Full credit for 13 entered

correctly (with credit off for incorrect entries):

 

Genera

Stains

Mycobacterium

 

Bacteroides

 

Bordetella

 

Borrelia

 

Campylobacter

 

Chlamydia

 

Corynebacterium

 

Enterobacter

 

Escherichia

 

Gardnerella

 

Haemophilus

 

Helicobacter

 

Klebsiella

 

Legionella

 

Moraxella

 

Mycoplasma

 

Neisseria

 

Pasteurella

 

Proteus

 

Pseudomonas

 

Rickettsia

 

Salmonella

 

Serratia

 

Shigella

 

Treponema

 

Vibrio

 

Yersinia

 

Bacillus

 

Clostridium

 

Staphylococcus

 

Streptococcus

 

Streptomyces

 

 

 

MOVEMENT ACROSS MEMBRANES

 

(21) Plasma membrane

(a)                    The plasma membrane of prokaryotes and eukaryotes are functionally equivalent, though the prokaryote plasma membrane additionally serves in roles that eukaryotes reserve for internal membranes (e.g., cellular respiration)

(b)                    Membranes consist of phospholipids which form into lipid bilayers because they have both a hydrophilic and a hydrophobic end

(c)                    These lipid bilayers are impermeable to charged or large substances (e.g., ions or sugars); they are thus said to be selectively permeable

(d)                    See Figure 4.7, The fluid mosaic model of the cell membrane

(e)                    [plasma membrane (Google Search)] [figure, cytoplasmic membrane (that fails to show asymmetry)] [index]

(22) Movement across membranes

(a)                    Small, hydrophobic substances typically can readily pass through plasma membranes by simple diffusion

(b)                    Passage of charged or large substances through lipid bilayers is mediated by integral membrane proteins

(c)                    Other proteins found in or on membranes serve as enzymes

(d)                    [movement across membranes (Google Search)] [index]

(23) Facilitated diffusion

(a)                    Movement of substances across membranes, with their concentration gradient (i.e., from areas of high concentration to areas of low concentration) and via facilitation by integral membrane proteins, is termed facilitated diffusion

(b)                    [facilitated diffusion (MicroDude)] [index]

(24) Active transport

(a)                    Movement of substances across membranes, against their concentration gradient (i.e., from areas of low concentration to areas of high concentration) via facilitation by integral membrane proteins, is termed active transport

(b)                    Note that active transport additionally is defined by a requirement for an expenditure of energy

(c)                    In a very real sense, active transport consists of a pumping of substances across membranes, thus increasing the substance's concentration on one side of the membrane

(d)                    [active transport (MicroDude)] [index]

(25) Cells are defined by the asymmetry of their membranes

(a)                    A cell functions in part as a consequence of the both the selective permeability of its membrane and the asymmetry of its membrane

(b)                    Asymmetry means that the two sides of the membrane do not fully resemble each other—and that the proteins associated with the membrane have a directionality so that there is an unambiguous inside of a protein as well as an unambiguous outside

(c)                    See Figure 4.7, The fluid mosaic model of the cell membrane

(d)                    Because of the cell membrane's asymmetry, cells allow or pump into their cytoplasm those substances they want to allow or pump in, and allow or pump out those substances that they want to get rid of

(e)                    Thus, a cell with an intact plasma membrane automatically (though typically with some expenditure of energy) carries out the processes necessary for the maintenance, growth, and replication of the cell

(f)                      [assymetry membrane (Google Search)] [index]

(26) Osmosis

(a)                    Osmosis is the movement of water into a cell by simple diffusion occurs from regions of high water concentration to regions of low water concentration

(b)                    Water's concentration may be lowered by dissolving substances in it

(c)                    The more that is dissolved in a water solution, the lower the concentration of water in that solution

(d)                    Across membranes, water naturally moves from regions of high water concentration to regions of low water concentration

(e)                    This movement is termed osmosis

(f)                      [osmosis -reverse, osmolarity, osmotic pressure, osmosis (Google Search)] [osmotic pressure (MicroDude)] [index]

(27) Tonicity

(a)                    "Tonicity describes the behavior of cells in a fluid environment."

(b)                    Essentially, there exist a series of terms that describe the solute concentration of a solution relative to the concentration exhibited by a reference solution (typically, outside of the cell relative to inside of the cell, with the latter the reference):

(i)                      Isotonic

(ii)                    Hypotonic

(iii)                   Hypertonic

(c)                    See Figure 4.31, Experiments that examine the effects of tonicity on osmosis

(d)                    [tonicity and osmolarity (Google Search)] [illustration, tonicity] [index]

(28) Isotonic

(a)                    An isotonic solution is one that has the same solute concentration as that displayed by the solution inside of a reference cell that is found suspended in the solution

(b)                    [isotonic and microbiology (Google Search)] [osmosis in isotonic environment] [index]

(29) Hypotonic

(a)                    A hypotonic solution is one that has a lower solute concentration than the reference cell's cytoplasm

(b)                    Red blood cells suspended in a hypotonic solution may burst following their osmotic uptake of water

(c)                    Cells with cell walls (including most bacteria, plants, and fungi) will resist taking in water and therefore will resist bursting

(d)                    [hypotonic and microbiology (Google Search)] [osmosis in hypertonic environment] [index]

(30) Hypertonic

(a)                    A hypertonic solution is one that has a higher solute concentration than the reference cell's cytoplasm

(b)                    Red blood cells suspended in hypertonic solutions tend to shrivel

(c)                    [hypertonic and microbiology (Google Search)] [osmosis in hypotonic environment] [index]

(31)  Cytoplasm

(a)                    The cytoplasm is simply the region of a bacterial cell that is internal to the plasma membrane

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

 

NUCLEIC ACIDS, AND THEIR PROTECTION

 

(32) Ribosomes

(a)                    Ribosomes are the organelles responsible for making proteins

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

(33) Nuclear region (nucleoid)

(a)                    This is simply where the bacterial DNA is located

(b)                    The nucleoid is not a membrane-enclosed region

(c)                    ["nuclear region" and bacteria, nucleoid and bacteria (Google Search)] [index]

(34) Endospores

(a)                    An endospore is a non-metabolizing bacterial cell that are highly resistant to numerous environment degradants including heat, drying, and all sorts of chemical insults

(b)                    Not all bacteria produce endospores

(c)                    Endospores are produced within bacterial cells (hence the endo- part of their name)

(d)                    Sporulation = endospore formation

(e)                    Germination = endospore conversion back to a vegetative (i.e., metabolizing/growing) bacterial cell

(f)                      Much of the elaborate efforts employed to sterilize bacteria media or instruments is employed to create conditions that are sufficiently harsh that even endospores are killed (and hence the media or instrument has been sterilized)

(g)                    [endospore (Google Search)] [endospore stain of genus Bacillus, endospore stain of Clostridium tetani, endospore cycle ß if you are having trouble understanding just what exactly an endospore is, then follow this series of cartoons depicting endospore formation (Biol 230 MicrobiologyGary E. Kaiser)] [“Jurassic Park” bacterium] [hey! better use a pressure cooker] [index]

 

BACTERIA EXTERNAL ANATOMY

 

(35) Flagella

(a)                    Attached to the cell envelope and projecting into the external environment are flagella

(b)                    These are long, thin, helical structures that are used like propellers to move bacteria

(c)                    See figure 4.13, Structure of two different bacterial flagella

(d)                    Note that bacteria flagella and eucaryotic flagella are not structurally similar

(e)                    Bacteria can have from one to many flagella, depending on bacterial species or strain

(f)                     See Figure 4.12, Arrangements of bacterial flagella

(g)                   

(h)                    [bacteria and flagella, flagellar arrangements (Google Search)] [what the heck is a bacterium’s tail? (Microbiology at KU and Jack's Place] [index]

(36) Atrichous

(a)                    Bacteria lacking flagella

(b)                    [atrichous (not much on bacteria out there) (Google Search)] [index]

(37) Monotrichous

(a)                    Bacilli with a single flagellum located at a pole

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

(38) Amphitrichous

(a)                    Bacilli with two flagella, one located at each pole

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

(39) Lophotrichous

(a)                    Bacilli with two or more flagella located at a single end or two or more each located at both ends (i.e., for former that would be at least two flagella and for the latter that would be at least four flagella)

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

(40) Peritrichous

(a)                    Bacilli with many flagella all over their surface

(b)                    [peritrichous (Google Search)] [image of peritrichous bacteria] [index]

(41) Axial filaments (endoflagella)

(a)                    Axial filaments are the spirochete equivalent of flagellum

(b)                    These are in contact with the spirochete cell envelope over their entire length and cause the entire spirochete bacterium to rotate and move as a corkscrew.

(c)                   

(d)                    [axial filaments, endoflagella (Google Search)] [index]

(42) Chemotaxis (positive chemotaxis, negative chemotaxis)

(a)                    Chemotaxis is the movement toward or away from a chemical stimulus

(b)                    This occurs via a “random walk” consisting of runs in which flagella propel the bacterium forward and twiddles in which opposite-turning flagella cause the bacteria to tumble

(c)                    Directed movement occurs because runs are longer in the direction in which the bacterium is attempting to move

(d)                    Movement towards a specific something an organism wants to mover towards is called  positive chemotaxis while movement away from a specific something an organism wants to avoid is called negative chemotaxis

(e)                    See Figure 4.14, Chemotaxis

(f)                     

(g)                    [chemotaxis and bacteria (Google Search)] [index]

(43) Phototaxis

(a)                    Movement towards light = positive phototaxis; away = negative phototaxis

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

(44) Pili

(a)                    A rigid, proteinaceous projection from the surface of bacterium that is used to attach the bacterium to various surfaces

(b)                    By allowing adherence to cells and tissue the existence of pili allows bacteria to be pathogenic against certain hosts (i.e., those organisms to which they can attach)

(c)                      

(d)                    [bacteria pili (Google Search)] [index]

(45) Glycocalyx

(a)                    Typically polysaccharide-containing secretions that collect around the bacterial cell surface

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

(46) Capsule

(a)                    A well organized bacterial glycocalyx that is firmly attached to the bacterial cell wall

(b)                    By protecting bacteria from host defenses capsules can contribute to the pathogenicity

(c)                    [bacterial capsule (Google Search)] [index]

(47) Slime layer

(a)                    Slime layers are a more-diffuse glycocalyx than capsules

(b)                    Slime layers protects cells from drying, serve to trap nutrients, or may bind cells together

(c)                    For example, Slime layers can trap nutrients and water, acting, for example, as a seal over a nutritious substrate, thus allowing a bacteria to use exoenzymes (extracellular enzymes) in a limited area containing high concentrations of substrate (i.e., to-be-digested nutrients)

(d)                    [slime layer (Google Search)] [index]

(48) Vocabulary [index]

(a)                    Active transport

(b)                    Amphitrichous

(c)                    Atrichous

(d)                    Axial filaments

(e)                    Bacillus

(f)                      Bacterial cell arrangements

(g)                    Bacterial cellular anatomy

(h)                    Bacterial shapes

(i)                      Capsule

(j)                      Cell wall

(k)                    Cells are defined by the asymmetry of their membranes

(l)                      Chemotaxis

(m)                  Classification of cells

(n)                    Coccobacillus

(o)                    Coccus

(p)                    Cytoplasm

(q)                    Diplo-

(r)                     Domains

(s)                     Endoflagella

(t)                      Endospores

(u)                    Endosymbiotic theory

(v)                    Endotoxin

(w)                  Eukaryotes

(x)                    Facilitated diffusion

(y)                    Flagella

(z)                     Glycocalyx

(aa)                 Gram-negative cell wall

(bb)                Gram-positive cell wall

(cc)                 Hypertonic

(dd)                Hypotonic

(ee)                 Inner membrane

(ff)                    Isotonic

(gg)                 Lipopolysaccharide

(hh)                 Lophotrichous

(ii)                     LPS

(jj)                    Monotrichous

(kk)                Movement across membranes

(ll)                     Negative chemotaxis

(mm)             Nuclear region

(nn)                 Nucleoid

(oo)                Osmosis

(pp)                Outer membrane

(qq)                Periplasm

(rr)                   Periplasmic space

(ss)                  Peritrichous

(tt)                    Phototaxis

(uu)                 Pili

(vv)                 Plasma membrane

(ww)             Pleomorphic

(xx)                 Positive chemotaxis

(yy)                 Prokaryotes

(zz)                  Protoplast

(aaa)             Ribosomes

(bbb)            Sarcina

(ccc)             Size of prokaryotes

(ddd)            Slime layer

(eee)             Spheroplast

(fff)                  Spirillum

(ggg)             Spirochete

(hhh)             Staphylo-

(iii)                   Strepto-

(jjj)                  Tetrad

(kkk)            Tonicity