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Microbial Physiology > Lecture 1A: Introduction to Microbial Physiology and Prokaryotic Cell Structures > Flashcards

Lecture 1A: Introduction to Microbial Physiology and Prokaryotic Cell Structures Flashcards

1
Q

Study of microbial cell functions which includes the study of microbial _________ , microbial ______________, and microbial _____________.

A
  • growth
  • metabolism
  • cell structure
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2
Q

how microbial cell structures, growth, and metabolism work in microorganisms.

A

microbial physiology

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3
Q

Bacteria which can synthesize their food. Ex: Algae, Cyanobacteria

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Autotrophs

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4
Q
  • Bacteria that cannot synthesize their food
  • Parasitic - They derive their food from living organisms
  • Saprophytic - They feed on dead and decaying organic matter
  • Symbiotic - They live in symbiotic association with other organisms

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Heterotrophs

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5
Q
  • how bacteria autotrophs produce their food
  • use chemicals such as CH4 or H2S and O2 to produce CO2 and energy.
A

Chemosynthesis

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6
Q

Microbial physiology is the __ relationships in microorganisms, especially how microbes respond to their environment.

A

structure-function

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7
Q

Microbial physiology is a foundational to advanced or applied fields such us __ and __.

2 examples

A
  • metabolic engineering
  • functional genomics
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8
Q

organisms that obtain energy from the oxidation of inorganic compounds

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

chemolithotrophs

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9
Q

Organisms that harvest energy by oxidizing organic chemicals

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Chemoorganotrophs

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10
Q

light and CO2

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Photoautotrophs

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11
Q

light and organic compounds

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Photoheterotrophs

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12
Q

chemical and co2

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Chemoautotrophs

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13
Q

chemical and organic componds

trophic classification system; how organisms obtain energy and carbon for growth and reproduction.

A

Chemoheterotrophs

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14
Q

Spherical or oval.

Give the name of the shape and 2 examples (genus)

A

Shape: Coccus (pl. cocci)
Example: Staphylococcus, Streptococcus

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15
Q

Rod-shaped.

Give the name of the shape and 2 examples (specific species)

A

Shape: Bacillus (pl. Bacilli)
Example: Escherichia coli, Bacillus subtilis

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16
Q

Spiral-shaped, rigid.

Give the name of the shape and 1 example (specific species)

A

Shape: Spirillum (pl. spirilla)
Example: Spirillum volutans

rat-bite fever

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17
Q

Spiral-shaped, flexible.

Give the name of the shape and 2 examples (specific species)

A

Shape: Spirochete
Example: Treponema pallidum, Borrelia burgdorferi

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18
Q

Comma-shaped (curved rod).

Give the name of the shape and 1 example (specific species)

A

Shape: Vibrio
Example: Vibrio cholerae

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19
Q

Long, thread-like.

Give the name of the shape and 2 examples (genus)

A

Shape: Filamentous
Example: Actinomyces, Streptomyces

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20
Q

Variable and irregular.

Give the name of the shape and 1 example (genus)

A

Shape: Pleomorphic
Example: Mycoplasma species

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21
Q

Definition: Bacteria that reproduce by budding, where a small portion of the cell forms a protrusion (bud) that eventually separates to become a new cell.
Key Feature: Formation of a bud, as opposed to binary fission (common in most bacteria).

give the bacteria and 2 examples (genus)

A
  • Budding bacteria
    Example:
  • Hyphomicrobium
  • Caulobacter (also appendaged)
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22
Q

Definition: Bacteria with extensions from their cells, such as stalks or prosthecae. These structures help in attachment to surfaces or nutrient absorption.
Key Features:
Stalks: Non-living, tubular extensions.
Prosthecae: Living extensions of the cell membrane and cytoplasm.
Holdfasts: Adhesive structures at the tips of stalks for surface attachment.

give the bacteria and 2 examples (genus)

A
  • Appendaged Bacteria
    Examples:
  • Caulobacter crescentus (Has a stalk and holdfast)
  • Gallionella (Produces stalk-like appendages)
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23
Q

Cocci arrangements:
1. Pairs
2. Chains
3. Clusters
4. Groups of four
5. Cubic arrangements of eight cells

name the arrangements

A
  1. Diplococci
  2. Streptococci
  3. Staphylococci
  4. Tetrads
  5. Sarcinae
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24
Q

Bacilli Arrangements:
1. Pairs of rods.
2. Chains of rods
3. Short, oval-shaped rods

A
  1. Diplobacilli
  2. Streptobacilli
  3. Coccobacilli
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25
Q

How wide is the bacterial cytoplasmic membrane?

A

8-10 nm wide

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26
Q

Morphology typically DOES NOT predict __, __, __, or other _____.

A
  • physiology
  • ecology
  • phylogeny
  • properties of a prokaryotic cell
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27
Q

There may be ___ involved in setting the morphology.

A

selective forces

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28
Q

Selective forces involved in setting the morphology (3)

A
  • optimization for nutrient uptake
  • swimming motility in vicious environments or near surfaces
  • gliding motility
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29
Q

What morphology is optimized for nutrient uptake?

A

Small cells with a high surface-to-volume ratio, such as appendaged cells.

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30
Q

What morphology aids in swimming motility in viscous environments or near surfaces?

A

Helical or spiral-shaped cells.

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31
Q

What morphology supports gliding motility?

A

Filamentous bacteria.

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32
Q

Size range for prokaryotes
| in diameter

A

0.2 μm to 700 μm in diameter

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33
Q

Most cultured rod-shaped bacteria are between __ and __ μm wide and __ μm long.

A
  • 0.5 and 4.0 μm
  • <15 μm
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34
Q

Examples of very large prokaryotes (2)

A
  • Epulopiscium fishelsoni (600 µm (0.6 mm) or more)
  • Thiomargarita namibiensis (10 mm long; can be seen in naked eye)

largest bacteria

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35
Q

Size range for eukaryotic cells

A

2 to >600 μm

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36
Q

Human resolution

in mm and μm (range)

A

0.001 mm
100 μm - 300 μm

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37
Q

Why is being small an advantage for cells?

Give 4 advantages

A
  • More surface area relative to cell volume (higher S/V ratio).
  • More surface area to take in nutrients and remove waste.
  • They process nutrients more efficiently.
  • Evolve faster; They mutate more quickly.
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38
Q

Cellular organisms __ μm in diameter are unlikely. It needs more volume to house proteins, nucleic acids, ribosomes, and so on.

Lower limits of cell size

A

<0.15 μm

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39
Q

Open oceans tend to contain small cells (__ to __ μm in diameter) known as “__”

A
  • 0.2 - 0.4 μm
  • ultramicrobacteria
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40
Q

Ultramicrobacteria genomes are highly __, missing functions that must be supplied by other microbes or hosts (plants or animals).

A

streamlined

straightforward; bare-minimum; obligate parasites; very few genes

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41
Q

In __ habitats in __, cells typically appear smaller in size than those of comparable __ habitats.

Is there a relationship between minimum size and environment?

A
  • low-nutrient
  • marine plankton
  • higher-nutrient
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42
Q
  • There may be a loose relationship between cell size and ambient nutrient concentration.
  • Still __ what function of naturally occurring small cells represent physiologically induced forms.

Is there a relationship between minimum size and environment?

A

unknown

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43
Q

New __ isolates grow well and maintain small cell size under relatively __.

Is there a relationship between minimum size and environment?

A
  • Verrucomicrobiales
  • low nutrient conditions
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44
Q

__ dwell (and are cultivated) in relatively nutrient-rich environments, yet maintain their small cell dimensions.

Is there a relationship between minimum size and environment?

A

Nanobacteria

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45
Q

__ and __ bacteria are known to have reduced __ capacities and __ sizes.

Is there a relationship between minimum size and environment?

A
  • symbiotic
  • parasitic
  • physiological
  • genome
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46
Q
  • What does the cytoplasmic membrane surround?
  • What does the cytoplasmic membrane separate the cytoplasm from?
A
  • cytoplasm
  • environment
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47
Q

What is the main function of the cytoplasmic membrane?

A

selective permeability

Allows nutrients in and waste products out.

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48
Q
  • Sterol-like molecules, strengthen the membrane in some bacterial species.
  • Provide structural support and stabilize the bacterial cytoplasmic membrane.
A

Hopanoid

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49
Q

What are the two types of proteins embedded in the cytoplasmic membrane? (2)

A

1) Integral membrane proteins: Significantly embedded in the membrane.
2) Peripheral membrane proteins: Loosely attached to the membrane.

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50
Q

What sterols are found in the cytoplasmic membranes of different organisms?
1) Humans
2) Plants
3) Fungi
4) Bacteria

A

1) Cholesterol
2) Sterol
3) Ergosterol
4) Hopanoids

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51
Q

Archaeal membranes have __ linkages in phospholipids of Archaea

A

ether

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52
Q

Bacteria and Eukarya have __ linkages in phospholipids

A

ester

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53
Q

Archaeal lipids have __ instead of __.

Archaeal membranes

A
  • isoprenoid
  • fatty acids
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54
Q

Major lipids are __ with branched __ side chains and __ __ with branched __ side chains, which can form lipid __.

Archaeal membrane

A
  • glycerol diether lipids
  • C20
  • glycerol tetraether lipids
  • C40
  • monolayers
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55
Q
  • A glycerol biphytanes glycerol tetraether (GDGT) biological membrane lipid. t - a lipid containing 5- and 6-carbon rings
  • A major lipid of Thaumarchaeota
  • slowly to melt; thermophilic microorganisms
  • form monolayer
A

Crenarchaeol

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56
Q

Give three (3) cytoplasmic membrane function

A
  • permeability barrier
  • protein anchor
  • energy conservation and consumption
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57
Q

Prevents leakage and functions as a gateway for transport of nutrients into, and wastes out of, the cell.

Functions of the cytoplasmic membrane

A

Permeability barrier

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58
Q

Site of proteins that participate in transport, bioenergetics, and chemotaxis.

Functions of the cytoplasmic membrane

A

Protein anchor

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59
Q

Site of generation and dissipation of the proton motive force.

Functions of the cytoplasmic membrane

A

Energy conservation

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60
Q

1) How do polar and charged molecules get through the membrane?
2) What do transport proteins do regarding solutes?

permeability barrier

A

1) They need transport proteins.
2) They help move solutes against the concentration gradient.

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61
Q

What is one function of the cytoplasmic membrane related to proteins?

A

It anchors transport proteins in place.

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62
Q

How does the cytoplasmic membrane help with energy?

A

It helps generate a proton motive force.

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63
Q

What happens to the rate of solute entry in facilitated diffusion as external concentration increases?

A

It increases until it reaches a maximum (Vmax) and then plateaus.

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64
Q

Why does facilitated diffusion plateau at Vmax?

A

Because the transport proteins can become saturated.

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65
Q

They move down their concentration gradient through specific carrier proteins or channels without energy.

What type of transport?

A

Facilitated diffusion

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66
Q

How does the rate of solute entry in active transport relate to external concentration?

A

It can maintain a steady influx of solutes against their concentration gradient, regardless of external concentration.

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67
Q

What is required for active transport to move solutes?

A

Energy, typically in the form of ATP.

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68
Q

What type of proteins are involved in active transport?

A

Specific pumps

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69
Q

How does the rate of solute entry in passive transport change with external concentration?

A

It increases until equilibrium is reached.

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70
Q

This transport can occur through simple diffusion without specific transport proteins for all solutes.

A

Passive transport

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71
Q

How do solutes move in passive transport?

A

They move down their concentration gradient without using energy.

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72
Q

How are species of bacteria classified based on Gram stain? (2)

A
  • Gram-positive
  • Gram-negative
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73
Q

The inventor of the Gram stain

A

Hans Christian Gram

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74
Q

What are the two main layers of a Gram-negative cell wall? (2)

A
  • Lipopolysaccharide (LPS) (outer membrane)
  • peptidoglycan
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75
Q

It is thicker and primarily consists of one layer of peptidoglycan.

A

Gram-positive cell wall

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76
Q

Is the cell membrane part of the bacterial cell wall?

A

No

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77
Q

Do all bacteria have a cell wall?

A

No

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78
Q

Do all bacteria with cell walls respond easily to Gram staining?

A

No

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79
Q

What is the main function of peptidoglycan?

A

provides strength as a rigid layer.

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80
Q

What are the two modified glucose components of peptidoglycan? (2)

A
  • N-acetylglucosamine (NAG)
  • N-acetylmuramic acid (NAM)
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81
Q

How are NAG and NAM linked in peptidoglycan?

A

linked in a β-1,4 linkage

82
Q

What amino acids are typically found in peptidoglycan? (5)

in order

A
  • L-alanine
  • D-glutamic acid
  • either L-lysine or diaminopimelic acid (DAP).
  • D-alanine
83
Q

Only __ have D-alanine amino acid.

A

prokaryotes

84
Q

Gram-positive bacteria often have “__” or __, while Gram-negative bacteria have different cross-linking.

A
  • interbridges
  • tetrapeptide bridges
85
Q
  • cleaves the glycosidic bond between sugars
  • cleaves β-1,4 linkage in peptidoglycan
86
Q

In human secretions, serving as a major defense against bacterial infections.

87
Q

How many distinct peptidoglycans have been described?

88
Q
  • It forms the backbone and is connected to peptide bridges that cross-link peptidoglycan chains.
  • It provides strength and rigidity to the cell wall.

What modified glucose?

A

N-acetylmuramic acid (NAM)

89
Q
  • __ is part of the peptidoglycan structure and alternates with __ in the chain.
  • does not form peptide bridges.

What modified glucose?

A
  • N-acetylglucosamine (NAG)
  • N-acetylmuramic acid (NAM)
90
Q

What is the main component of the gram-positive cell wall?

A

Up to 90% peptidoglycan.

91
Q
  • Acidic substances attached to peptidoglycan.
  • They bind divalent metal ions (e.g., __,__) for transport.
  • not attached to lipids
A
  • Teichoic acids
  • Ca²⁺, Mg²⁺
92
Q
  • Teichoic acids attached to the cell membrane.
  • They extend through the peptidoglycan layer and anchor to the cytoplasmic membrane.
  • attached to lipids
A

lipoteichoic acids

93
Q

What type of prokaryotes lack cell walls? (2)

A
  • mycoplasma
  • thermoplasma
94
Q

1) A group of pathogenic bacteria related to gram-positives that lack cell walls.
2) An archaeon that lacks a cell wall.

A

1) mycoplasma
2) thermoplasma

95
Q

What additional components do thermoplasma have? (2)

A
  • Hopanoids
  • lipoglycans
96
Q

What do Archaea have instead of cell walls?

A

Tough cytoplasmic membranes containing sterols or lipoglycans.

97
Q

composition of the cell wall in gram-negative bacteria:
It contains a small amount of __ and mostly comprises the __ and __ layers.

A
  • peptidoglycan
  • outer membrane
  • lipopolysaccharide (LPS)
98
Q

The outer membrane serves in gram-negative bacteria and acts as a barrier against __ and other __.

A
  • antibiotics
  • harmful agents
99
Q

What are the components of lipopolysaccharide (LPS)? (3)

A
  • core polysaccharide
  • O-polysaccharide
  • lipid A
100
Q

Lipopolysaccharide replaces most of the __ in the outer half of the outer membrane.

A

phospholipids

101
Q
  • the toxic component of LPS and is considered an endotoxin.
  • integral to the cell and is never released.
102
Q

Lipid A can cause harmful effects when present in the body, as seen with pathogens like __ and __

Give 2 examples

A
  • Pseudomonas
  • E. coli.
103
Q

What is an example of an exotoxin?

A

Staphylococcus toxin

104
Q

It is composed of repeating units and varies among strains, especially in Gram-negative bacteria, contributing to their antigenic diversity.

Component of LPS

A

O-Specific Polysaccharide

105
Q

Its variability among strains contributes to the antigenic diversity of these bacteria.

Component of LPS

A

O-Specific polysaccharide

106
Q

It contains around 67 carbon sugars, including KDO, which is unique to bacteria.

Component of LPS

A

Core Polysaccharide

107
Q
  • A sugar unique to bacteria
  • critical for linking the polysaccharide components to the lipid bilayer of the bacterial membrane.
A

KDO

3-Deoxy-d-manno-octulosonic Acid

108
Q

found in some gram-negative cell walls, is one of the most abundant membrane proteins

A

Braun lipoprotein

109
Q

space located between cytoplasmic and outer membranes

110
Q

transmembrane protein channels for entrance and exit of solutes

111
Q

Do Archaeal cell walls contain peptidoglycan?

112
Q

It is a polysaccharide similar to peptidoglycan found in the cell walls of certain methanogenic Archaea.

A

pseudopeptidoglycan (pseudomurein)

113
Q

What are the components of pseudopeptidoglycan? (2)

Archaea

A
  • N-acetylglucosamine (NAG)
  • N-acetyltalominuronic acid (NAT) with glycosidic bonds.
114
Q

All amino acids in pseudopeptidoglycan are __.

Archaea

115
Q

Archaeal cell walls resistant to __ and __ because they contain __ glycosidic bonds instead of the __ bonds found in bacterial peptidoglycan.

A
  • lysozyme
  • penicillin
  • β-1,3
  • β-1,4
116
Q

Do all Archaea have pseudopeptidoglycan?

117
Q

Do all Archaea have a cell wall?

118
Q

Is pseudopeptidoglycan present in all Archaeal cell walls?

119
Q

1) What do the cell walls of some Archaea contain instead of pseudomurein?
2) The most common cell wall type in Archaea, consisting primarily of protein or glycoprotein; act as a “cell wall,” providing structure and protection.

A
  • other polysaccharide polymers
  • S-layers
120
Q

What is the structure of S-layers?

A

paracrystalline structure

121
Q

In many organisms, S-layers are present in __ to other cell wall components, usually polysaccharides.

122
Q

What is the position of the S-layer on the cell wall?

A

outermost layer

123
Q

Not considered part of the cell wall because these do not confer significant structural strength.

Cell surface structures (2)

A

Capsules and slime layers

124
Q

Capsules and slime layers
- Assist in __ to surfaces
- Has a role in the development and maintenance of __.
- Virulence factors: protect against __.
- Prevent __/__

Cell surface structures

A
  • attachment
  • biofilms
  • phagocytosis
  • dehydration/desiccation
125
Q
  • a tightly organized matrix that excludes small particles and is firmly/tighlty attached to the bacterial cell.
  • can be visualized by light microscopy with India ink or by electron microscopy.

Cell surface structures

126
Q

Loosely attached, easily deformed, does not exclude small particles, and is more difficult to see microscopically.

Cell surface structures

A

Slime layers

127
Q

What bacterial species commonly forms slime layers?

Cell surface structures

A

lactic acid bacterium Leuconostoc

128
Q

Thick layer of bacterial cells that forms on solid surfaces, facilitated by extracellular polysaccharides.

Cell surface structures

129
Q

How do capsules contribute to bacterial pathogenicity?
Capsules act as __ by preventing the immune system from recognizing and destroying the bacteria.

Cell surface structures

A
  • virulence factors
130
Q

Give an example of bacteria with a thick capsule. (2)

Cell surface structures

A
  • Bacillus anthracis (protein capsule)
  • Streptococcus pneumoniae (polysaccharide capsule).
131
Q

How do bacterial outer surface layers protect cells in dry environments?

Cell surface structures

A

They bind water, preventing desiccation.

132
Q

longer, fewer in number, and involved in specific functions like genetic exchange and adhesion.

Cell surface structures

A

Pili (pilus)

133
Q

Which types of bacteria produce pili?

Cell surface structures

A

All gram-negative bacteria and many gram-positive bacteria.

134
Q

Two types of pili

Cell surface structures

A
  • Conjugative/sex pili
  • Type IV pili
135
Q

Involved in conjugation, facilitating genetic exchange between bacterial cells.

Cell surface structures; what type of pili?

A

Conjugative/sex pili

136
Q
  • Enable twitching motility, a gliding movement where pili extend, attach to a surface, and retract to pull the cell forward.
  • They mediate genetic transformation, one of three horizontal gene transfer methods alongside conjugation and transduction.

Cell surface structures; what type of pili?

A

Type IV pili

137
Q

Name bacteria that use twitching motility via Type IV pili. (2)

Cell surface structures

A
  • Pseudomonas species
  • Moraxella species
138
Q

What human pathogens use Type IV pili for colonization? (3)

Cell surface structures

A
  • Vibrio cholerae (cholera)
  • Neisseria gonorrhoeae (gonorrhea)
  • Streptococcus pyogenes (strep throat and scarlet fever)
139
Q

A unique attachment structure in some Archaea, resembling a grappling hook, used for forming biofilms.

Cell surface structures

A

hamus (plural: hami)

140
Q

Which Archaea group forms hami? (inhabits anoxic groundwater in Earth’s deep subsurface, used to trap nutrients)

Cell surface structures

A

SM1 Archaeal group

141
Q

In nutrient-limited habitats, they affix cells to surfaces and to each other, preventing them from being washed away and aiding in nutrient trapping.

Cell surface structures

A

hamus (plural: hami) of SM1 Archaeal group

142
Q

Hami and Type IV pili are filamentous structures, but hami have a __ for attachment.

Cell surface structures

A

barbed terminus

143
Q

__ are structures in prokaryotic cells that serve as energy reserves, carbon reservoirs, or have specialized functions, enclosed by a __, and reduces __.

Cell surface structures

A
  • Cell inclusions
  • thin membrane
  • osmotic stress
144
Q

Why is storing substances in an insoluble form advantageous for cells?

Cell surface structures

A

reduces osmotic stress in the cytoplasm

145
Q

Give five (5) cell inclusions

Cell surface structures

A
  • carbon storage polymers (poly-β-hydroxybutyric acid (PHB), PHA (generic term) and Glycogen
  • Polyphosphate granules
  • sulfur globules (or granules)
  • carbonate minerals
  • magnetosomes
146
Q

What’s the most common inclusion in prokaryotes?

Cell surface structures; Give two (2) classes

A

Carbon storage polymers
- poly-β-hydroxybutyric acid (PHB), PHA (generic term)
- Glycogen

147
Q

A lipid inclusion/lipid polymer formed from β-hydroxybutyric acid units, used for carbon and energy storage.

Cell surface structures

A

poly-β-hydroxybutyric acid (PHB)

148
Q

PHB granules formed by the __ of β-hydroxybutyric acid monomers through __ linkages, aggregating into visible granules.

Cell surface structures

A
  • polymerization
  • ester
149
Q

A class of carbon-storage polymers that vary in monomer length from C3 to C18.

Cell surface structures

A

poly-β-hydroxyalkanoate (PHA)

150
Q

poly-β-hydroxyalkanoates (PHAs) are synthesized during __ carbon and broken down as carbon or energy sources when __.

Cell surface structures

A
  • excess
  • needed
151
Q

A glucose polymer that serves as a carbon and energy reservoir, produced during carbon excess.

Cell surface structures

152
Q

Glycogen has a slightly different __between glucose units compared to starch.

Cell surface structures

153
Q

Inclusions that store inorganic phosphate (PO4³⁻) and supply it for biosynthesis or ATP production.

Cell surface structures

A

polyphosphate granules

154
Q

They store elemental sulfur (S⁰), which is oxidized to sulfate (SO₄²⁻) when sulfur sources become limiting.

Cell surface structures

A

sulfur granules

in sulfur-oxidizing bacteria

155
Q

Where are sulfur granules located in cells?

Cell surface structures; in what type of prokaryotes?

A

Periplasm

in gram-negative bacteria and Archaea

156
Q

The microbiological process of forming minerals, such as carbonate minerals, within or on cells.

Cell surface structures

A

biomineralization

157
Q

What type of carbonate mineral is formed by Gloeomargarita lithophora?

Cell surface structures; what does it contain? (3)

A

Benstonite, containing barium, strontium, and magnesium.

158
Q

Intracellular carbonate minerals in cyanobacteria may act as ballast or a way to __ __ for autotrophic growth.

Cell surface structures

A

sequester carbonate

159
Q
  • Inclusions containing magnetic iron oxides, such as magnetite or greigite, allowing bacteria to orient within magnetic fields.
  • Can orient with the magnetic field of the Earth

Cell surface structures

A

Magnetosomes

160
Q

The process by which bacteria migrate along Earth’s magnetic field lines using magnetosomes.

Cell surface structures

A

magnetotaxis

161
Q

Magnetosomes synthesized through __ formation in the __ membrane, followed by __ accumulation and __.

Cell surface structures

A
  • vesicle
  • cytoplasmic
  • iron
  • biomineralization
162
Q

What is the common shape of magnetosomes? (3)

Cell surface structures

A
  • Square
  • rectangular
  • spike-shaped

depending on the species.

163
Q

Protein-based, hollow, conical-shaped structures in some bacteria and archaea that confer buoyancy, allowing cells to float in the water column.

Cell structures

A

Gas vesicles

164
Q

Gas vesicles confer __ in platonic cells. They are conical-shaped, gas-filled structures made of __. Also, impermeable to __.

Cell structures

A
  • buoyancy
  • protein
  • water and solutes
165
Q

Which microorganisms commonly contain gas vesicles?

Cell structures; where are they often found?

A

Planktonic bacteria and archaea, such as cyanobacteria

which often form blooms in lakes and other water bodies.

166
Q

The primary function of gas vesicles is to enable cells to position themselves in regions of the water column that best suit their __, such as areas with __ for photosynthesis.

Cell structure

A
  • metabolism
  • optimal light
167
Q

Gas vesicles are less dense than the cell __, reducing the overall __ of the cell and allowing it to __.

Cell structure

A
  • cytoplasm
  • density
  • float
168
Q

Gas vesicles are made of two proteins: (2)

Cell structure

A
  • GvpA (Gas vesicle protein A)
  • GvpC (Gas vesicle protein C)
169
Q
  • The major protein that forms the rigid, watertight vesicle shell.
  • A hydrophobic, rigid, and aligns to form parallel ribs that create a watertight and pressure-resistant shell.
  • Structure: Beta (β) sheets

Cell structure: Gas Vesicles

A

GvpA (Gas vesicle protein A)

170
Q
  • A minor protein that strengthens the shell by cross-linking GvpA molecules.
  • Strengthens the gas vesicle shell by binding and cross-linking the ribs formed by GvpA molecules.
  • Structure: alpha (α) helix

Cell structure: Gas Vesicles

A

GvpC (Gas vesicle protein C)

171
Q

Gas vesicles be observed using __ microscopy, where clusters of vesicles (gas vacuoles) appear as irregular bright inclusions, or through __ microscopy.

Cell structures

A
  • light
  • transmission electron
172
Q

Gas vesicles impermeable to water and solutes but permeable to gases to maintain the __ composition while preventing water or solutes from collapsing the __ structure.

Cell structure

A
  • internal gas
  • vesicle
173
Q

What happens to buoyancy when gas vesicles collapse?

Cell structure

A

loses buoyancy and sinks in the water column

174
Q

__ important for phototrophic bacteria because they allow the bacteria to adjust their position in the water column to regions with optimal light for photosynthesis.

Cell structure

A

Gas vesicles

175
Q

What is the process of endospore formation called?

A

Endosporulation (or sporulation).

176
Q

What is the primary function of endospores?

A

Survival in unfavorable growth conditions.

177
Q

What environmental conditions can endospores resist? (3)

A
  • Heat
  • harsh chemicals
  • radiation
178
Q

What are the two major genera of endospore-forming bacteria? (2)

A
  • Bacillus
  • Clostridium
179
Q

Endospore is present only in gram-__ bacteria.

180
Q

What diseases are caused by endospore-forming bacteria? (3)

A
  • Botulism (Clostridium botulinum)
  • tetanus (Clostridium tetani)
  • foodborne infections

botulism=rare, serious illness;toxin attacks the body’s nerves

181
Q

When do bacterial cells begin sporulation?

A

When key nutrients (e.g., carbon or nitrogen) become limiting.

182
Q

What are the three steps of endospore germination? (3)

A
  • Activation
  • germination
  • outgrowth

mn: AGO

183
Q

Endospore’s ideal for dispersal is via (3)

A
  • wind
  • water
  • animal gut

|mn: disp(ER)salWWA

184
Q

What triggers endospore activation?

A

Heating for several minutes at an elevated but sublethal temperature.

185
Q

What signals endospore germination? (2)

A

rapid (minutes)
- loss of refractility
- resistance to heat and chemicals.

refractile-cell has components that absorb light at variable amounts and reflect light at different amounts.

186
Q

What occurs during outgrowth? (3)

A
  • swelling from water uptake
  • RNA/protein/DNA synthesis
  • vegetative cell emergence
187
Q

What are the endospore structure/features/layers (from outermost to innermost)? (5)

A

Exosporium → Spore coats → Cortex → Core wall → Core (DNA)

mn: EX→SPO→CO→CO→COD

188
Q

What is the main composition of the cortex?

A

Loosely cross-linked peptidoglycan

189
Q

What molecule is found in endospores but not in vegetative cells?

A

Dipicolinic acid (DPA)

190
Q

Dehydrates the endospore and stabilizes DNA against heat.

|Endospores

A

Dipicolinic acid (DPA)

191
Q

What ion is complexed with dipicolinic acid?

|Endospores

A

Calcium (Ca²⁺)

192
Q

What is the percentage of the calcium–dipicolinic acid complex in the endospore’s dry weight?

193
Q

Why do endospores have lower water content than vegetative cells? (2)

A

To increase heat resistance and enzyme inactivity.

194
Q

What temperature kills most bacterial endospores?

A

121°C (autoclave temperature)

195
Q

What proteins protect endospore DNA from UV radiation and desiccation? It functions as carbon and energy source for outgrowth.

A

Small acid-soluble spore proteins (SASPs)

196
Q

How do SASPs protect DNA from UV damage?

A

They convert DNA from the “B” form to the more compact “A” form.

197
Q

Highly differentiated, dormant bacterial cells that are resistant to heat, chemicals, and radiation.

198
Q

How many spore-specific genes are involved in sporulation?

A

Over 200 spore-specific genes.

199
Q

How many bacterial genera are known to form endospores?

A

Nearly 20 genera.

Microbial Physiology (5 decks)

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