What intracellular granules does the unicellular cyanobacterium Gloeomargarita form?
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What intracellular granules does the unicellular cyanobacterium Gloeomargarita form?
Granules of benstonite, a carbonate mineral containing barium, strontium, and magnesium.
What is a major difference between the outer membrane (OM) and the cell membrane (CM) in bacteria?
The presence of polysaccharide molecules covalently bound to lipids in the outer membrane.
What is the glycocalyx?
A sticky coat of polysaccharide formed outside of the cell envelope.
What are fimbriae, pili, and hami?
Fimbriae and pili are hair-like structures on the surface of bacteria, while hami resemble tiny grappling hooks and are found in the SM1 group of Archaea.
What potential functions do the granules of benstonite serve for Gloeomargarita?
They might function as ballast to maintain cell position or sequester carbonate to support autotrophic growth.
What are porins?
Transmembrane proteins that allow nonspecific transport of solutes across the outer membrane.
What is the function of hami?
Hami attach cells to surfaces and to each other due to their barbed terminus.
What distinguishes a capsule from a slime layer?
A capsule is organized in a tight matrix and excludes small particles, while a slime layer is loosely attached and does not exclude particles.
Which type of bacteria has an outer membrane?
Gram-negative bacteria.
What is polar flagellation?
Flagella are attached at one or both ends of a cell.
What are gas vesicles and their function in cyanobacteria?
Structures that confer buoyancy, allowing cells to position themselves in optimal regions of the water column.
What type of movement occurs in peritrichously flagellated bacteria when no attractant is present?
Random movement.
What is Poly-β-hydroxybutyric acid (PHB)?
PHB is a carbon storage polymer that can vary in length and is synthesized by cells when there is an excess of carbon.
What is required to produce a capsule in the lab?
Sucrose.
What role do cations like Ca2+ and Mg2+ play in the outer membrane?
They neutralize the negatively charged membrane and contribute to its mechanical strength.
What is lophotrichous flagellation?
A type of polar flagellation where a tuft of many flagella arises at one end of the cell.
What are cyanobacterial blooms?
Massive accumulations of cyanobacteria on or near the lake surface where sunlight is most intense for maximal photosynthesis.
How do peritrichously flagellated bacteria respond to an increase in attractant concentration?
Runs become longer and tumbles less frequent.
What is the periplasm?
A space of about 15 nm located between the outer surface of the cytoplasmic membrane and the inner surface of the outer membrane.
How is glycogen related to carbon storage?
Glycogen is a polymer of glucose produced when carbon is in excess, serving as a carbon and energy storage polymer.
What role does the glycocalyx play in bacterial pathogens?
It contributes to infectivity and prevents dehydration by binding water.
What is the shape of flagella in bacteria?
Flagella are not just straight, but also helical.
What is Lipid A?
A component of lipopolysaccharides that acts as an endotoxin and is a virulence factor for certain bacteria.
What is amphitrichous flagellation?
Flagellation where a tuft of flagella emerges from both poles of the cell.
What is the permeability characteristic of gas vesicles?
Impermeable to water and solutes but permeable to gases.
What is a key difference in microscopic appearance between vegetative cells and endospores?
Vegetative cells are nonrefractile, while endospores are refractile.
What happens to the movement of bacteria when the concentration of attractant decreases?
Runs become shorter and tumbles more frequent.
What types of proteins reside in the periplasm?
Hydrolytic enzymes, binding proteins, and chemoreceptors.
What is the role of polyphosphate in cells?
Polyphosphate serves as a source of phosphate for nucleic acid and phospholipid biosynthesis when phosphate is limiting.
What are fimbriae?
Short pili that mediate attachment.
What are the components of the flagellum motor in gram-negative bacteria?
The L ring, P ring, MS ring, and C ring.
What are the functions of lipopolysaccharides (LPS)?
Facilitate surface recognition, act as virulence factors, and contribute to the mechanical strength of the cell.
What are endospores?
Highly differentiated dormant cells that protect the bacterial genome and function as survival structures.
What characterizes peritrichous flagellation?
Flagella are inserted around the cell surface.
What are magnetosomes and their significance?
Biomineralized particles of magnetic iron oxides that allow bacteria to orient themselves within a magnetic field.
What is the calcium content in vegetative cells compared to endospores?
Vegetative cells have low calcium content, while endospores contain a calcium-dipicolinic acid complex.
What is the function of hydrolytic enzymes in the periplasm?
They initiate the degradation of polymeric substances.
How can polyphosphate be utilized in energy metabolism?
Polyphosphate can be broken down to synthesize the energy-rich compound ATP from ADP.
What are the functions of pili?
They can mediate conjugation, act as nanowires, and facilitate twitching motility.
What is the significance of the core polysaccharide in LPS?
It is present in all gram-negative bacteria and is part of the lipopolysaccharide structure.
What are chemoreceptors?
Membrane proteins that sense attractants and repellents and transduce this information to flagella.
What environmental conditions can endospores tolerate?
Extreme heat, radiation, chemical exposure, drying, and nutrient depletion.
What does atrichous mean?
A bacterium without flagella.
What are S-layers and where are they found?
S-layers are found in many Bacteria (5-20 nm) and in nearly all Archaea (70 nm).
What is magnetotaxis?
The process of migrating along Earth's magnetic field lines.
How does the enzymatic activity differ between vegetative cells and endospores?
Vegetative cells have high enzymatic activity, whereas endospores have low enzymatic activity.
How do binding proteins function in the periplasm?
They begin the process of transporting substrates, similar to ABC transporters.
What anchors the L ring in gram-negative bacteria?
The outer membrane.
What are sulfur granules and their function?
Sulfur granules are formed from the oxidation of sulfide and are involved in oxidizing reduced sulfur compounds, generating electrons for energy metabolism.
What is the diameter range of pili?
2–10 nm.
What are exotoxins?
Toxins produced by microorganisms and released outside, distinct from endotoxins like Lipid A.
How do polarly flagellated bacteria reorient themselves?
By relying on Brownian motion when stopped.
Are endospores reproductive structures?
No, they are dormant stages of a bacterial life cycle, not reproductive structures like fungal spores.
What is monotrichous flagellation?
A bacterium with a singular flagella at the polar end of the cell.
What role do S-layers play in Archaea?
They can take the role of the cell wall, providing structural strength, protecting from osmotic lysis, and conferring cell shape.
What initiates the sporulation cycle in bacteria?
Asymmetric cell division occurs when nutrients deplete or conditions are unfavorable.
What role do chemoreceptors play in microorganisms?
They govern the chemotaxis response.
What is the heat resistance level of endospores compared to vegetative cells?
Endospores have high heat resistance, while vegetative cells have low heat resistance.
What is the function of the stator in the flagellum motor?
It surrounds the inner rings and is anchored in the cytoplasmic membrane and peptidoglycan.
What is a biofilm?
A clump of microorganisms that can form on solid surfaces, facilitated by the glycocalyx.
What is a chemotaxis assay?
A method where a small glass capillary tube is immersed into a suspension of motile bacteria to create a chemical gradient.
What is sporulation?
The process of cellular differentiation of vegetative cells that results in endospore formation.
How do peritrichous flagella contribute to cell movement?
They form a bundle at one end and rotate counterclockwise (CCW) for forward motion.
How do S-layers help prevent osmotic lysis?
The cell wall prevents lysis by maintaining high internal pressure due to concentrated solutes.
What is hydrotaxis?
Movement with respect to a gradient of available water.
What separates the DNA forespore from the mother cell during sporulation?
The forespore is separated by an outer spore membrane.
What are porins?
Proteins that function as channels for the entrance and exit of solutes in the outer membrane.
What role do small acid-soluble spore proteins (SASPs) play in endospores?
SASPs bind tightly to DNA, protecting it from damage and stabilizing it for survival in harsh conditions.
How does the rotation of the flagellum occur?
At the expense of the proton motive force.
What is osmotaxis?
Movement with respect to a gradient of ionic strength, such as salt concentration.
How does a flagellar filament grow?
It grows from the tip, not from its base.
What is the main component of the flagellum filament?
Many copies of a protein called flagellin.
What additional functions do S-layers serve?
They facilitate cell surface interactions, such as attachment, and can increase the ability of some bacterial pathogens to cause disease.
Can endospores revert back into vegetative cells?
Yes, endospores can remain dormant for years but can revert back rapidly.
What is aerotaxis?
Movement with respect to gradients of O2.
What is formed around the forespore during late sporulation?
Cortex, which lays down layers of calcium and dipicolinic acid.
What is the composition of the cortex in endospores?
The cortex is composed of peptidoglycan.
How many protons are translocated by each rotation of the flagellum?
About 1200 protons.
What is the difference between nonspecific and specific porins?
Nonspecific porins form water-filled channels for very small hydrophilic substances, while specific porins contain a binding site for one or a group of structurally related substances.
What is required for twitching motility?
Type IV pili, which extend from one pole of the cell, attach to a surface, and then retract to pull the cell forward.
What is the response of peritrichously flagellated bacteria to a repellent?
Longer runs are triggered by a decrease in concentration of the repellent.
How many flagellin protein molecules are needed to make one flagellar filament?
Approximately 20,000.
What is the function of the hook in the flagellum?
It connects the filament to the flagellum motor in the basal body.
What is unique about the cell envelope of methanogenic Archaea?
They have cell walls made of pseudomurein that may or may not have an outer S-layer.
What is the first step in the reversion of an endospore to a vegetative cell?
Activation, where the spore becomes less refractile as it is hydrated.
What is phototaxis?
Movement with respect to a gradient in light intensity.
What occurs during the maturation phase of the sporulation cycle?
Formation of the outermost exosporium of the endospore.
What is the function of the calcium-dipicolinic acid complex in endospores?
It binds water, dehydrates the endospore, and stabilizes DNA against heat denaturation.
What is the first step in flagellar synthesis?
The MS ring is synthesized first and inserted into the cytoplasmic membrane.
What are some classes of antibiotics that target cell wall synthesis?
Beta-lactams, glycopeptides, and bacitracin.
What provides the energy for twitching motility?
ATP hydrolysis.
What happens if a flagellum is broken?
It can still rotate and be repaired with new flagellin units passed through the filament channel.
What happens during clockwise (CW) rotation of polar flagella?
The cell moves backward.
What happens during germination of an endospore?
The spore begins to develop into a vegetative cell, typically a rapid process.
What distinguishes the outer membrane of Ignococcus?
It is composed largely of archaeal isoprenoid lipids and lacks LPS.
What do phototrophic purple bacteria do in response to light?
They move preferentially toward certain wavelengths of light.
What is germination in the context of the sporulation cycle?
The process that occurs when living conditions improve.
What is the water content in vegetative cells compared to endospores?
Vegetative cells have high water content (80-90%), while endospores have low water content (10-25%).
What role do cap proteins play in flagellar synthesis?
They assist flagellin molecules to assemble in the proper fashion at the flagellum tip.
How can bacteria develop resistance to antibiotics?
By producing proteins that bind to antibiotics like beta-lactams or by evolving to the dosages of antibiotics.
Which bacterium is known for biofilm formation through twitching motility?
Pseudomonas (a gram-negative bacterium).
What are archaella?
The flagella counterpart in archaea, composed of proteins unrelated to those of flagella.
How do Mycoplasmas adapt to their environment?
They contain sterols in their cytoplasmic membranes to add strength and rigidity, experiencing little osmotic pressure when living within another cell.
What is the final stage of endospore reversion?
Outgrowth, where the vegetative cell emerges and begins to divide.
What is scotophobotaxis?
Swimming into darkness outside the illuminated field of view; response only to the absence of light.
What are plasmids?
Extrachromosomal DNA found in bacteria, often in hundreds within a cell.
What is the core of an endospore composed of?
The core contains DNA and ribosomes.
What type of secretion system facilitates the synthesis of the flagellum?
A type III secretion system.
What is unique about Mycoplasmas in terms of cell structure?
They have an absence of a cell wall and contain sterols and lipoglycans in their cytoplasmic membrane.
What are the two types of motility exhibited by Myxobacteria?
Social motility (caused by twitching) and adventurous motility (caused by gliding).
How do archaella differ from flagella in terms of structure?
Archaella are smaller, not hollow, and are assembled from their bases with a center filled with proteins.
What indicates the lack of refractility during germination?
It signals that the spore is developing into a vegetative cell.
How do plasmids replicate?
They can exist and replicate independently of the chromosome or may be integrated with it.
What is the role of photoreceptors in bacteria?
They sense a gradient of light and interact with cytoplasmic proteins that control flagellar rotation in chemotaxis.
What facilitates movement in groups for Myxobacteria?
Type IV pili and the secretion of extracellular polysaccharides.
What drives the movement of archaella?
ATP hydrolysis, unlike flagella which are driven by proton motive force.
What advantages do plasmids confer to bacteria?
They can carry genes for drug resistance, pathogenicity, and new metabolic activities.
What do aerobic organisms require for optimal movement?
They require O2 and may swim toward increasing concentrations of it.
How does gliding motility differ from twitching?
Gliding is a smooth motion along the long axis of a cell without external propulsive structures.
How do the swimming speeds of archaea compare to bacteria?
Archaea swim much more slowly than bacteria.
What structure allows bacteria to swim?
Flagellum (plural, flagella).
What is the typical O2 concentration for microaerophiles?
Usually between 1% and 5% O2.
What type of bacteria typically exhibit gliding motility?
Filamentous or rod-shaped bacteria.
What is the significance of surface motility in bacteria?
It results in distinctive colony morphology as cells can move out and away from the center of the colony.
What is the analogous structure to flagella found in Archaea?
Archaellum.
What are magnetosomes?
Specialized structures found in magnetotactic bacteria that allow them to align with magnetic field lines.
What drives the 'gliding motors' in gliding bacteria?
The proton motive force.
What is an example of a gliding bacterium?
Flavobacterium johnsoniae gliding away from the center of the colony.
What are bacterial flagella described as?
Tiny rotating machines that push or pull the cell through a liquid.
Why are antibiotics targeting the outer membrane not effective against all bacteria?
Because gram-positive bacteria do not have an outer membrane.
What is chemotaxis?
A response to chemicals.
What is the width range of archaella?
About 10–13 nm.
What is the typical width of bacterial flagella?
15–20 nm, depending on the species.
How does the cell envelope serve as a site of energy conservation in prokaryotes?
It houses enzymes and proteins involved in oxidative phosphorylation and the electron transport chain, facilitating the creation of a proton motive force.
What behavior do cells exhibit during chemotaxis?
A biased random walk toward the attractant.
Why is the cell membrane described as a fluid mosaic model?
It describes the random arrangement of carbohydrate molecules across the cell surface, giving a fluid-like appearance.
What is phototaxis?
A response to light, typically seen in filamentous cyanobacteria.
