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
2
Q
how microbial cell structures, growth, and metabolism work in microorganisms.
A
microbial physiology
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
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
5
Q
- how bacteria autotrophs produce their food
- use chemicals such as CH4 or H2S and O2 to produce CO2 and energy.
A
Chemosynthesis
6
Q
Microbial physiology is the __ relationships in microorganisms, especially how microbes respond to their environment.
A
structure-function
7
Q
Microbial physiology is a foundational to advanced or applied fields such us __ and __.
2 examples
A
- metabolic engineering
- functional genomics
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
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
10
Q
light and CO2
trophic classification system; how organisms obtain energy and carbon for growth and reproduction.
A
Photoautotrophs
11
Q
light and organic compounds
trophic classification system; how organisms obtain energy and carbon for growth and reproduction.
A
Photoheterotrophs
12
Q
chemical and co2
trophic classification system; how organisms obtain energy and carbon for growth and reproduction.
A
Chemoautotrophs
13
Q
chemical and organic componds
trophic classification system; how organisms obtain energy and carbon for growth and reproduction.
A
Chemoheterotrophs
14
Q
Spherical or oval.
Give the name of the shape and 2 examples (genus)
A
Shape: Coccus (pl. cocci)
Example: Staphylococcus, Streptococcus
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
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
17
Q
Spiral-shaped, flexible.
Give the name of the shape and 2 examples (specific species)
A
Shape: Spirochete
Example: Treponema pallidum, Borrelia burgdorferi
18
Q
Comma-shaped (curved rod).
Give the name of the shape and 1 example (specific species)
A
Shape: Vibrio
Example: Vibrio cholerae
19
Q
Long, thread-like.
Give the name of the shape and 2 examples (genus)
A
Shape: Filamentous
Example: Actinomyces, Streptomyces
20
Q
Variable and irregular.
Give the name of the shape and 1 example (genus)
A
Shape: Pleomorphic
Example: Mycoplasma species
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)
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)
23
Q
Cocci arrangements:
1. Pairs
2. Chains
3. Clusters
4. Groups of four
5. Cubic arrangements of eight cells
name the arrangements
A
- Diplococci
- Streptococci
- Staphylococci
- Tetrads
- Sarcinae
24
Q
Bacilli Arrangements:
1. Pairs of rods.
2. Chains of rods
3. Short, oval-shaped rods
A
- Diplobacilli
- Streptobacilli
- Coccobacilli
25
How wide is the bacterial cytoplasmic membrane?
8-10 nm wide
26
Morphology typically DOES NOT predict __, __, __, or other _____.
- physiology
- ecology
- phylogeny
- properties of a prokaryotic cell
27
There may be ___ involved in setting the morphology.
selective forces
28
Selective forces involved in setting the morphology (3)
- optimization for nutrient uptake
- swimming motility in vicious environments or near surfaces
- gliding motility
29
What morphology is optimized for nutrient uptake?
Small cells with a high surface-to-volume ratio, such as appendaged cells.
30
What morphology aids in swimming motility in viscous environments or near surfaces?
Helical or spiral-shaped cells.
31
What morphology supports gliding motility?
Filamentous bacteria.
32
Size range for prokaryotes
| in diameter
0.2 μm to 700 μm in diameter
33
Most cultured rod-shaped bacteria are between __ and __ μm wide and __ μm long.
- 0.5 and 4.0 μm
- <15 μm
34
Examples of very large prokaryotes (2)
- *Epulopiscium fishelsoni* (600 µm (0.6 mm) or more)
- *Thiomargarita namibiensis* (10 mm long; can be seen in naked eye)
| largest bacteria
35
Size range for eukaryotic cells
2 to >600 μm
36
Human resolution
| in mm and μm (range)
0.001 mm
100 μm - 300 μm
37
Why is being small an advantage for cells?
| Give 4 advantages
- 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.
38
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
<0.15 μm
39
Open oceans tend to contain small cells (__ to __ μm in diameter) known as "__"
- 0.2 - 0.4 μm
- ultramicrobacteria
40
Ultramicrobacteria genomes are highly __, missing functions that must be supplied by other microbes or hosts (plants or animals).
streamlined
| straightforward; bare-minimum; obligate parasites; very few genes
41
In __ habitats in __, cells typically appear smaller in size than those of comparable __ habitats.
| Is there a relationship between minimum size and environment?
- low-nutrient
- marine plankton
- higher-nutrient
42
- 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?
unknown
43
New __ isolates grow well and maintain small cell size under relatively __.
| Is there a relationship between minimum size and environment?
- Verrucomicrobiales
- low nutrient conditions
44
__ dwell (and are cultivated) in relatively nutrient-rich environments, yet maintain their small cell dimensions.
| Is there a relationship between minimum size and environment?
Nanobacteria
45
__ and __ bacteria are known to have reduced __ capacities and __ sizes.
| Is there a relationship between minimum size and environment?
- symbiotic
- parasitic
- physiological
- genome
46
- What does the cytoplasmic membrane surround?
- What does the cytoplasmic membrane separate the cytoplasm from?
- cytoplasm
- environment
47
What is the main function of the cytoplasmic membrane?
selective permeability
| Allows nutrients in and waste products out.
48
- Sterol-like molecules, strengthen the membrane in some bacterial species.
- Provide structural support and stabilize the bacterial cytoplasmic membrane.
Hopanoid
49
What are the two types of proteins embedded in the cytoplasmic membrane? (2)
1) **Integral membrane proteins**: Significantly embedded in the membrane.
2) **Peripheral membrane proteins**: Loosely attached to the membrane.
50
What sterols are found in the cytoplasmic membranes of different organisms?
1) Humans
2) Plants
3) Fungi
4) Bacteria
1) Cholesterol
2) Sterol
3) Ergosterol
4) Hopanoids
51
Archaeal membranes have __ linkages in phospholipids of Archaea
ether
52
Bacteria and Eukarya have __ linkages in phospholipids
ester
53
Archaeal lipids have __ instead of __.
| Archaeal membranes
- isoprenoid
- fatty acids
54
Major lipids are __ with branched __ side chains and __ __ with branched __ side chains, which can form lipid __.
| Archaeal membrane
- glycerol diether lipids
- C20
- glycerol tetraether lipids
- C40
- monolayers
55
- 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
Crenarchaeol
56
Give three (3) cytoplasmic membrane function
- permeability barrier
- protein anchor
- energy conservation and consumption
57
Prevents leakage and functions as a gateway for transport of nutrients into, and wastes out of, the cell.
| Functions of the cytoplasmic membrane
Permeability barrier
58
Site of proteins that participate in transport, bioenergetics, and chemotaxis.
| Functions of the cytoplasmic membrane
Protein anchor
59
Site of generation and dissipation of the proton motive force.
| Functions of the cytoplasmic membrane
Energy conservation
60
1) How do polar and charged molecules get through the membrane?
2) What do transport proteins do regarding solutes?
| permeability barrier
1) They need transport proteins.
2) They help move solutes against the concentration gradient.
61
What is one function of the cytoplasmic membrane related to proteins?
It anchors transport proteins in place.
62
How does the cytoplasmic membrane help with energy?
It helps generate a proton motive force.
63
What happens to the rate of solute entry in **facilitated diffusion** as external concentration increases?
It increases until it reaches a **maximum (Vmax)** and then **plateaus**.
64
Why does facilitated diffusion plateau at Vmax?
Because the **transport proteins** can become **saturated**.
65
They move down their concentration gradient through specific carrier proteins or channels without energy.
| What type of transport?
Facilitated diffusion
66
How does the rate of solute entry in **active transport** relate to external concentration?
It can maintain a **steady influx of solutes** against their concentration gradient, regardless of external concentration.
67
What is required for active transport to move solutes?
Energy, typically in the form of ATP.
68
What type of proteins are involved in active transport?
Specific pumps
69
How does the rate of solute entry in **passive transport** change with external concentration?
It increases until equilibrium is reached.
70
This transport can occur through simple diffusion without specific transport proteins for all solutes.
Passive transport
71
How do solutes move in passive transport?
They move down their concentration gradient without using energy.
72
How are species of bacteria classified based on Gram stain? (2)
- Gram-positive
- Gram-negative
73
The inventor of the Gram stain
Hans Christian Gram
74
What are the two main layers of a Gram-negative cell wall? (2)
- Lipopolysaccharide (LPS) (outer membrane)
- peptidoglycan
75
It is thicker and primarily consists of one layer of peptidoglycan.
Gram-positive cell wall
76
Is the cell membrane part of the bacterial cell wall?
No
77
Do all bacteria have a cell wall?
No
78
Do all bacteria with cell walls respond easily to Gram staining?
No
79
What is the main function of peptidoglycan?
provides strength as a rigid layer.
80
What are the two modified glucose components of peptidoglycan? (2)
- N-acetylglucosamine (NAG)
- N-acetylmuramic acid (NAM)
81
How are NAG and NAM linked in peptidoglycan?
linked in a **β-1,4 linkage**
82
What amino acids are typically found in peptidoglycan? (5)
| in order
- L-alanine
- D-glutamic acid
- either L-lysine or diaminopimelic acid (DAP).
- D-alanine
83
Only __ have D-alanine amino acid.
prokaryotes
84
Gram-positive bacteria often have "__" or __, while Gram-negative bacteria have different cross-linking.
- interbridges
- tetrapeptide bridges
85
- cleaves the glycosidic bond between sugars
- cleaves β-1,4 linkage in peptidoglycan
Lysozyme
86
In human secretions, serving as a major defense against bacterial infections.
Lysozyme
87
How many distinct peptidoglycans have been described?
100+
88
- 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?
N-acetylmuramic acid (NAM)
89
- __ is part of the peptidoglycan structure and alternates with __ in the chain.
- does not form peptide bridges.
| What modified glucose?
- N-acetylglucosamine (NAG)
- N-acetylmuramic acid (NAM)
90
What is the main component of the gram-positive cell wall?
Up to 90% peptidoglycan.
91
- Acidic substances attached to peptidoglycan.
- They bind divalent metal ions (e.g., __,__) for transport.
- not attached to lipids
- Teichoic acids
- Ca²⁺, Mg²⁺
92
- Teichoic acids attached to the cell membrane.
- They extend through the peptidoglycan layer and anchor to the cytoplasmic membrane.
- attached to lipids
lipoteichoic acids
93
What type of prokaryotes lack cell walls? (2)
- mycoplasma
- thermoplasma
94
1) A group of pathogenic bacteria related to gram-positives that lack cell walls.
2) An archaeon that lacks a cell wall.
1) mycoplasma
2) thermoplasma
95
What additional components do thermoplasma have? (2)
- Hopanoids
- lipoglycans
96
What do Archaea have instead of cell walls?
Tough cytoplasmic membranes containing sterols or lipoglycans.
97
composition of the cell wall in gram-negative bacteria:
It contains a small amount of __ and mostly comprises the __ and __ layers.
- peptidoglycan
- outer membrane
- lipopolysaccharide (LPS)
98
The outer membrane serves in gram-negative bacteria and acts as a barrier against __ and other __.
- antibiotics
- harmful agents
99
What are the components of lipopolysaccharide (LPS)? (3)
- core polysaccharide
- O-polysaccharide
- lipid A
100
Lipopolysaccharide replaces most of the __ in the outer half of the outer membrane.
phospholipids
101
- the toxic component of LPS and is considered an endotoxin.
- integral to the cell and is never released.
Lipid A
102
Lipid A can cause harmful effects when present in the body, as seen with pathogens like __ and __
| Give 2 examples
- *Pseudomonas*
- *E. coli.*
103
What is an example of an exotoxin?
*Staphylococcus* toxin
104
It is composed of repeating units and varies among strains, especially in Gram-negative bacteria, contributing to their antigenic diversity.
| Component of LPS
O-Specific Polysaccharide
105
Its variability among strains contributes to the antigenic diversity of these bacteria.
| Component of LPS
O-Specific polysaccharide
106
It contains around 67 carbon sugars, including KDO, which is unique to bacteria.
| Component of LPS
Core Polysaccharide
107
- A sugar unique to bacteria
- critical for linking the polysaccharide components to the lipid bilayer of the bacterial membrane.
KDO
| 3-Deoxy-d-manno-octulosonic Acid
108
found in some gram-negative cell walls, is one of the most abundant membrane proteins
Braun lipoprotein
109
space located between cytoplasmic and outer membranes
periplasm
110
transmembrane protein channels for entrance and exit of solutes
porins
111
Do Archaeal cell walls contain peptidoglycan?
No
112
It is a polysaccharide similar to peptidoglycan found in the cell walls of certain methanogenic Archaea.
pseudopeptidoglycan (pseudomurein)
113
What are the components of pseudopeptidoglycan? (2)
| Archaea
- N-acetylglucosamine (NAG)
- N-acetyltalominuronic acid (NAT) with glycosidic bonds.
114
All amino acids in pseudopeptidoglycan are __.
| Archaea
L-isomers
115
Archaeal cell walls resistant to __ and __ because they contain __ glycosidic bonds instead of the __ bonds found in bacterial peptidoglycan.
- lysozyme
- penicillin
- β-1,3
- β-1,4
116
Do all Archaea have pseudopeptidoglycan?
No
117
Do all Archaea have a cell wall?
No
118
Is pseudopeptidoglycan present in all Archaeal cell walls?
No
119
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.
- other polysaccharide polymers
- S-layers
120
What is the structure of S-layers?
paracrystalline structure
121
In many organisms, S-layers are present in __ to other cell wall components, usually polysaccharides.
addition
122
What is the position of the S-layer on the cell wall?
outermost layer
123
Not considered part of the cell wall because these do not confer significant structural strength.
| Cell surface structures (2)
Capsules and slime layers
124
**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
- attachment
- biofilms
- phagocytosis
- dehydration/desiccation
125
- 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
Capsule
126
Loosely attached, easily deformed, does not exclude small particles, and is more difficult to see microscopically.
| Cell surface structures
Slime layers
127
What bacterial species commonly forms slime layers?
| Cell surface structures
lactic acid bacterium *Leuconostoc*
128
Thick layer of bacterial cells that forms on solid surfaces, facilitated by extracellular polysaccharides.
| Cell surface structures
biofilm
129
How do capsules contribute to bacterial pathogenicity?
Capsules act as __ by preventing the immune system from recognizing and destroying the bacteria.
| Cell surface structures
- virulence factors
130
Give an example of bacteria with a thick capsule. (2)
| Cell surface structures
- *Bacillus anthracis* (protein capsule)
- *Streptococcus pneumoniae* (polysaccharide capsule).
131
How do bacterial outer surface layers protect cells in dry environments?
| Cell surface structures
They bind water, preventing desiccation.
132
longer, fewer in number, and involved in specific functions like genetic exchange and adhesion.
| Cell surface structures
Pili (pilus)
133
Which types of bacteria produce pili?
| Cell surface structures
**All** gram-negative bacteria and **many** gram-positive bacteria.
134
Two types of pili
| Cell surface structures
- Conjugative/sex pili
- Type IV pili
135
Involved in conjugation, facilitating genetic exchange between bacterial cells.
| Cell surface structures; what type of pili?
Conjugative/sex pili
136
- 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?
Type IV pili
137
Name bacteria that use twitching motility via Type IV pili. (2)
| Cell surface structures
- *Pseudomonas* species
- *Moraxella* species
138
What human pathogens use Type IV pili for colonization? (3)
| Cell surface structures
- *Vibrio cholerae* (cholera)
- *Neisseria gonorrhoeae* (gonorrhea)
- *Streptococcus pyogenes* (strep throat and scarlet fever)
139
A unique attachment structure in some Archaea, resembling a grappling hook, used for forming biofilms.
| Cell surface structures
hamus (plural: hami)
140
Which Archaea group forms hami? (inhabits anoxic groundwater in Earth's deep subsurface, used to trap nutrients)
| Cell surface structures
SM1 Archaeal group
141
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
hamus (plural: hami) of SM1 Archaeal group
142
Hami and Type IV pili are filamentous structures, but hami have a __ for attachment.
| Cell surface structures
barbed terminus
143
__ are structures in prokaryotic cells that serve as energy reserves, carbon reservoirs, or have specialized functions, enclosed by a __, and reduces __.
| Cell surface structures
- Cell inclusions
- thin membrane
- osmotic stress
144
Why is storing substances in an insoluble form advantageous for cells?
| Cell surface structures
**reduces osmotic stress** in the cytoplasm
145
Give five (5) cell inclusions
| Cell surface structures
- carbon storage polymers (poly-β-hydroxybutyric acid (PHB), PHA (generic term) and Glycogen
- Polyphosphate granules
- sulfur globules (or granules)
- carbonate minerals
- magnetosomes
146
What's the most common inclusion in prokaryotes?
| Cell surface structures; Give two (2) classes
Carbon storage polymers
- poly-β-hydroxybutyric acid (PHB), PHA (generic term)
- Glycogen
147
A lipid inclusion/lipid polymer formed from β-hydroxybutyric acid units, used for carbon and energy storage.
| Cell surface structures
poly-β-hydroxybutyric acid (PHB)
148
PHB granules formed by the __ of β-hydroxybutyric acid monomers through __ linkages, aggregating into visible granules.
| Cell surface structures
- polymerization
- ester
149
A class of carbon-storage polymers that vary in monomer length from C3 to C18.
| Cell surface structures
poly-β-hydroxyalkanoate (PHA)
150
poly-β-hydroxyalkanoates (PHAs) are synthesized during __ carbon and broken down as carbon or energy sources when __.
| Cell surface structures
- excess
- needed
151
A glucose polymer that serves as a carbon and energy reservoir, produced during carbon excess.
| Cell surface structures
glycogen
152
Glycogen has a slightly different __between glucose units compared to starch.
| Cell surface structures
linkage
153
Inclusions that store inorganic phosphate (PO4³⁻) and supply it for biosynthesis or ATP production.
| Cell surface structures
polyphosphate granules
154
They store elemental sulfur (S⁰), which is oxidized to sulfate (SO₄²⁻) when sulfur sources become limiting.
| Cell surface structures
sulfur granules
| in sulfur-oxidizing bacteria
155
Where are sulfur granules located in cells?
| Cell surface structures; in what type of prokaryotes?
Periplasm
| in gram-negative bacteria and Archaea
156
The microbiological process of forming minerals, such as carbonate minerals, within or on cells.
| Cell surface structures
biomineralization
157
What type of carbonate mineral is formed by *Gloeomargarita lithophora*?
| Cell surface structures; what does it contain? (3)
**Benstonite**, containing barium, strontium, and magnesium.
158
Intracellular carbonate minerals in cyanobacteria may act as ballast or a way to __ __ for autotrophic growth.
| Cell surface structures
sequester carbonate
159
- 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
Magnetosomes
160
The process by which bacteria migrate along Earth’s magnetic field lines using magnetosomes.
| Cell surface structures
magnetotaxis
161
Magnetosomes synthesized through __ formation in the __ membrane, followed by __ accumulation and __.
| Cell surface structures
- vesicle
- cytoplasmic
- iron
- biomineralization
162
What is the common shape of magnetosomes? (3)
| Cell surface structures
- Square
- rectangular
- spike-shaped
| depending on the species.
163
Protein-based, hollow, conical-shaped structures in some bacteria and archaea that confer buoyancy, allowing cells to float in the water column.
| Cell structures
Gas vesicles
164
Gas vesicles confer __ in platonic cells. They are conical-shaped, gas-filled structures made of __. Also, impermeable to __.
| Cell structures
- buoyancy
- protein
- water and solutes
165
Which microorganisms commonly contain gas vesicles?
| Cell structures; where are they often found?
**Planktonic bacteria** and **archaea**, such as cyanobacteria
| which often form blooms in lakes and other water bodies.
166
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
- metabolism
- optimal light
167
Gas vesicles are less dense than the cell __, reducing the overall __ of the cell and allowing it to __.
| Cell structure
- cytoplasm
- density
- float
168
Gas vesicles are made of two proteins: (2)
| Cell structure
- GvpA (Gas vesicle protein A)
- GvpC (Gas vesicle protein C)
169
- 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
GvpA (Gas vesicle protein A)
170
- 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
GvpC (Gas vesicle protein C)
171
Gas vesicles be observed using __ microscopy, where clusters of vesicles (gas vacuoles) appear as irregular bright inclusions, or through __ microscopy.
| Cell structures
- light
- transmission electron
172
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
- internal gas
- vesicle
173
What happens to buoyancy when gas vesicles collapse?
| Cell structure
**loses buoyancy** and **sinks** in the water column
174
__ 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
Gas vesicles
175
What is the process of endospore formation called?
Endosporulation (or sporulation).
176
What is the primary function of endospores?
Survival in unfavorable growth conditions.
177
What environmental conditions can endospores resist? (3)
- Heat
- harsh chemicals
- radiation
178
What are the two major genera of endospore-forming bacteria? (2)
- *Bacillus*
- *Clostridium*
179
Endospore is present only in gram-__ bacteria.
positive
180
What diseases are caused by endospore-forming bacteria? (3)
- Botulism (*Clostridium botulinum*)
- tetanus (*Clostridium tetani*)
- foodborne infections
| botulism=rare, serious illness;toxin attacks the body's nerves
181
When do bacterial cells begin sporulation?
When key nutrients **(e.g., carbon or nitrogen)** become limiting.
182
What are the three steps of endospore germination? (3)
- Activation
- germination
- outgrowth
| mn: AGO
183
Endospore's ideal for dispersal is via (3)
- wind
- water
- animal gut
|mn: disp(**ER**)sal**WWA**
184
What triggers endospore **activation**?
**Heating** for several minutes at an elevated but **sublethal temperature**.
185
What signals endospore **germination**? (2)
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
What occurs during **outgrowth**? (3)
- swelling from water uptake
- RNA/protein/DNA synthesis
- vegetative cell emergence
187
What are the endospore structure/features/layers (from outermost to innermost)? (5)
Exosporium → Spore coats → Cortex → Core wall → Core (DNA)
| mn: EX→SPO→CO→CO→COD
188
What is the main composition of the cortex?
Loosely cross-linked peptidoglycan
189
What molecule is found in endospores but not in vegetative cells?
Dipicolinic acid (DPA)
190
Dehydrates the endospore and stabilizes DNA against heat.
|Endospores
Dipicolinic acid (DPA)
191
What ion is complexed with dipicolinic acid?
|Endospores
Calcium (Ca²⁺)
192
What is the percentage of the calcium–dipicolinic acid complex in the endospore’s dry weight?
About 10%
193
Why do endospores have lower water content than vegetative cells? (2)
To **increase heat resistance** and **enzyme inactivity**.
194
What temperature kills most bacterial endospores?
121°C (autoclave temperature)
195
What proteins protect endospore DNA from UV radiation and desiccation? It functions as carbon and energy source for outgrowth.
Small acid-soluble spore proteins (SASPs)
196
How do SASPs protect DNA from UV damage?
They **convert** DNA from the "B" form to the **more compact "A" form.**
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Highly differentiated, dormant bacterial cells that are resistant to heat, chemicals, and radiation.
Endospore
198
How many spore-specific genes are involved in sporulation?
Over 200 spore-specific genes.
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How many bacterial genera are known to form endospores?
Nearly 20 genera.
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