Microbiology Chapter 3 Assignment

Evaluate the statements below and choose those that would constitute growth factors in bacterial cells.

-cysteine -adenine -thymine -nicotinic acid -folic acid

Before the understanding of bacteria and archaea as distinct domains, certain characteristics were used to define prokaryotes. Select the cell components that were believed to be lacking before genetic and genomic analyses proved otherwise.

-cytoskeleton -Golgi apparatus -plasma membrane Prokaryotic cells were originally separated from eukaryotic cells due to being simpler. Prokaryotes were said to be lacking a membrane bound nucleus, membrane bound organelles, a cytoskeleton, and membranous cytoplasmic structures such as the endoplasmic reticulum and Golgi apparatus.

Peripheral Proteins

-easily extracted -loosely connected to cell membrane -soluble in aqueous solution -30% of membrane proteins

Slime layer

-easily removed -diffuse (unorganized) -facilitates motility

Flagellum

responsible for locomotion

Sex pilus

responsible for transferring DNA from one bacterial cell to another

Gram-positive bacteria have flagella with four basal body rings, while those of Gram-negative bacteria have only two. (T/F)

False

In an endospore, the protein coat forms a layer external to the exosporium. (T/F)

False

Germination is one process by which bacterial cells can reproduce. (T/F)

False Germination refers to an endospore taking on water and returning to a vegetative state and becoming an active bacterium. It is a form of bacterial survival not reproduction.

Match the terms listed to the type of bacteria they best describe: Gram-positive or Gram-negative.

Final Gram stain color - Purple Gram-Positive Bacteria Sensitivity to lysozyme - Not sensitive to lysozyme Gram-Negative Bacteria Lipopolysaccharide - LPS present Gram-Negative Bacteria Outer membrane - Outer membrane absent Gram-Positive Bacteria Relative thickness of peptidoglycan - Thin peptidoglycan Gram-Negative Bacteria Sensitivity to penicillin - More sensitive to penicillin Gram-Positive Bacteria Sensitivity to lysozyme - Sensitive to lysozyme Gram-Positive Bacteria Final Gram stain color - Pink Gram-Negative Bacteria Lipopolysaccharide - LPS absent Gram-Positive Bacteria Teichoic acids - Teichoic acids absent Gram-Negative Bacteria Outer membrane - Outer membrane present Gram-Negative Bacteria Teichoic acids - Teichoic acids present Gram-Positive Bacteria Sensitivity to penicillin - Less sensitive to penicillin Gram-Negative Bacteria Relative thickness of peptidoglycan - Thick peptidoglycan Gram-Positive Bacteria

Which of the following bacterial structures are most directly linked to swimming motility in chemotaxis?

Flagella

Review your understanding of the factors that influence the size and shape of a bacterial cell by completing each sentence.

In bacteria, as the surface area-to-volume ratio increases, nutrient uptake becomes more efficient. A cocci with the same volume as a rod has a lower S/V ratio than does the rod. A rod with the same S/V ratio as a cocci can have greater nutrient uptake across its cytoplasmic membrane than the cocci. Epulopiscium fishelsoni has a highly convoluted plasma membrane to increase its S/V ratio to compensate for its large size. The surface to volume ratio (S/V ratio) is influenced by the size and shape of the cell. The higher the S/V ratio the more efficient diffusion and nutrient uptake into the cell becomes.

Review your understanding of different types of cytoplasmic inclusions in bacterial cells by completing each sentence below.

Inclusions containing carbon are most commonly in the form of poly-beta-hydroxybutyrate and can be commercially used to create biodegradable plastics. Nucleic acids are synthesized from inorganic inclusions called polyphosphate granules, while specialized photosynthetic bacteria can store energy as sulfur globules. Another type of inclusion, which photosynthetic microbes often use to store carbon dioxide and the enzyme RuBisCO, is the carboxysome. Finally, buoyancy in aquatic bacteria is mediated by gas vacuoles, while certain bacteria accumulate magnetite in magnetosomes that can detect natural magnetic fields.

Which of the following is a component of the outer membrane in Gram-negative bacteria that results in septic shock upon entering the bloodstream?

Lipopolysaccharide Lipopolysaccharide contains a chemical region that triggers an inflammatory reaction that can lead to septic shock. If high amounts of LPS enters the bloodstream it can become a lethal response.

Pick the definition of simple diffusion from the answers below.

Movement of molecules from areas of higher concentration to areas of lower concentration

When analyzing the outer membrane of Gram-negative bacteria, which part of lipopolysaccharide induces an antibody response?

O-antigen The O side chain of LPS is also called the O antigen because it elicits an antibody response by the infected host.

Bacteria contain several types of cytoskeletal proteins. Match the protein with its function within the cell.

ParA: segregates chromosomes and plasmids FtsZ: Cell division MreB: Helps determine shape of cell Bactofilin: protein and chromosome positioning

Fimbriae

Responsible for bacterial attachment to surfaces

Gliding motility in bacteria involves which of the following?

Specialized cell-surface proteins and slimy polysaccharides

Lophtrichous

several flagella extending from one cell "pole" to power locomotion Flagella arrangements can be used in taxonomy and reveals different microbial adaptations to environmental challenges.

Many bacteria have overcome the difficulty of iron uptake by secreting low molecular weight iron-binding proteins called _________

siderophores Siderophores are low molecular weight iron-binding proteins produced by bacteria in order to bind and take up iron for use in the cell. Iron is very insoluble so special transport methods are required.

Conjugative plasmids

transfer DNA from one cell to another

The rate of diffusion of a molecule into a cell is affected by which of the following factors?

Steep concentration gradient with a high amount of the molecule outside the cell

Review your understanding of the cell wall structure in Gram-negative bacteria by completing each sentence.

The cell wall of Gram-negative bacterial cells is external to the plasma membrane. This structure contains only a thin layer of peptidoglycan. In addition, there is a(n) outer membrane external to the Gram-negative bacterial peptidoglycan layer. The two-layer cell wall of Gram-negative bacteria is separated from the plasma membrane by the periplasmic space. The addition of alcohol during the Gram-staining procedure causes decolorization of Gram-negative bacteria and the addition of safranin results in pink cells.

Which of the following statements is FALSE when comparing bacterial and eukaryotic cytoskeletal proteins?

The cytoskeletal proteins found in bacterial cells are structurally and functionally unrelated to those found in eukaryotic cells. (IS FALSE)

Which statement about flagellar structure is TRUE?

The filament extends out of the cell.

Complete bacterial ribosomes are comprised of approximately 55 proteins and three molecules of ribosomal RNA. (T/F)

True

Spirochetes move in a screw-like manner that is mediated by bundles of flagella located in the cell's periplasmic space.

True

Spore formation is initiated when there is a scarcity of nutrients. (T/F)

True

When observing flagella distribution patterns, bacteria with a single flagellum at each pole are called _________ bacteria.

amphitrichous Amphitrichous bacteria (amphi means on both sides) have a single flagellum at each pole.

The bacterial flagellum moves _________.

by rotation that is powered by the proton motive force

R plasmids

carry antibiotic resistance genes

Metabolic plasmids

carry genes for enzymes

Virulence plasmids

carry virulence genes

Amphitrichous

two flagella extend from two different cell "poles" to power locomotion Flagella arrangements can be used in taxonomy and reveals different microbial adaptations to environmental challenges.

Col plasmids

produce bacteriocins

The bacterial flagellum is driven to rotate by protons moving down a charge and pH gradient and the energy provided is called the

proton motive force Proton movement down a charge and pH gradient generated by the electron transport chain releases energy that is used to rotate the flagellum and is called the proton motive force.

Select the statements below that correctly apply to characteristics of bacterial cell permeability.

-Is a barrier to passive diffusion of large compounds -Has presence of aquaporins

Nearly all bacteria contain peptidoglycan. Review the structure of peptidoglycan by selecting the correct characteristics listed below.

-Polymer of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) -Contains D-amino acids not found in proteins Peptidoglycan is composed of alternating NAG and NAM residues. Many bacteria cross-link the strands by connecting the carboxyl group of the D-alanine at position 4 directly to the amino group of diaminopimelic acid (position 3) of the other strand. Other bacteria use a peptide interbridge instead. The peptidoglycan sacculus is strong but elastic.

Review the properties of endospores that allow them to survive adverse environmental conditions by selecting protective properties of the endospore core below.

-core has a slightly acidic pH -core has low water content -core has high amounts of dipicolinic acid complexed with calcium ions

Macroelements are required in relatively large amounts by the cell. Select all of the characteristics of macroelements to review their importance to the cell.

-examples are oxygens, hydrogen, and carbon -some exist as cations -can contribute to molecule stability Macroelements are required in relatively large amounts by the cell. They are found in organic molecules such as proteins, lipids, nucleic acids, and carbohydrates. Other macroelements are potassium, calcium, magnesium, and iron. They exist as cations and generally are associated with and contribute to the activity and stability of molecules and cell structures such as enzymes and ribosomes.

Integral Proteins

-not easily extracted -embedded in cell membrane -insoluble in aqueous solutions -70% of membrane proteins

Capsule

-not easily removed -well organized -helps resist phagocytosis

In the Gram-positive bacterial cell wall, the tetrapeptides that extend from the peptidoglycan layers are linked by _________blank.

-peptide interbridges

Activation is a process that prepares spores for germination and can result from treatments such as heating. This is followed by germination, which begins when proteins called germinant receptors detect small molecules such as sugars or amino acids. Eventually water levels inside the germinating spore reach that of vegetative cells. Enzymes in the core become active and synthesis of the various molecules needed to initiate spore outgrowth to a vegetative state are made.

...

Iron is required by bacteria for metabolic activities. Put the following steps in order to review the bacterial method of iron uptake for the cell.

1. Iron scarce in environment 2. Bacteria secretes siderophore 3. Iron-siderophore complex binds cell surface protein 4. Iron-siderophore complex enters cell via ABC transporter

Place the steps of endospore formation in their proper order by matching the descriptive statement to the proper stage in the image.

1. axial filament formation 2. septum formation 3. engulfment of forespore 4. cortex formation 5. coat synthesis 6. coat completion 7. lysis and spore liberation

Evaluate the paragraph that discusses bacterial ribosomes and choose the correct answer from each of the choices given.

Bacterial cells contain thousands of ribosomes that carry out translation. Some are located in the cytoplasm and others are attached to the plasma membrane. The bacterial ribosome is smaller than those found in eukaryotes. It is designated as a 70s ribosome. When discussing a ribosome's size, the "s" stands for Svedberg unit; a measure of how fast a particle travels when centrifuged. The greater the number, the faster it travels. The number of proteins associated with the bacterial ribosome is well characterized; there are approximately 55 proteins total— 21 in the small subunit and 34 in the large.

Review your understanding of nucleoid organization by choosing the correct word/phrase to complete each sentence.

Bacterial chromosomes are longer than the cell, so the genetic material must be tightly packaged. Nucleoid-associated proteins bind to the DNA via covalent bonds that cause the DNA to bend and fold. The chromosome has several levels of structural organization, including macrodomains, chromosome interaction domains, and supercoiling. During binary fission, DNA binding proteins play an important role in compacting the daughter chromosomes to ensure proper replication as the cell divides.

Why is boiling at standard temperature and pressure an inadequate method of processing for canned foods?

Boiling to 100°C will kill vegetative C. botulinum cells, but any spores will survive to temperatures of 120°C.

Select the true statements with respect to the use of the term "prokaryote."

Both bacteria and archaea have cytoskeletal components It is preferable to define an organism by what it contains, rather than what it lacks. Bacteria and archaea are genetically distinct from each other.

Match the following bacterial cytoplasmic structures with their function to review the bacterial cell.

Cytoskeleton: Involved in cell division and controlling cell shape Ribosome: Involved in protein synthesis Chromosome: contains genetic information required for survival Gas vesicle: contains compounds that aid in buoyancy Endospore: a dormant cell state Storage granules: contains high-molecular weight polymers plasmid: extrachromosomal DNA molecules

Bacterial endospores are protected from chemicals and various lytic enzymes due to the presence of the spore layer called the _________.

coat The ability of the spore to survive heat, radiation, and damaging chemicals requires that its enzymes and DNA be protected. The various layers of the spore contribute to this resistance in several ways. The spore coat protects the spore from chemicals and various lytic enzymes.

Outgrowth

core enzymes become active due to increased water levels

The spore layer containing peptidoglycan is the _________

cortex

The movement of dissolved solutes from a region of higher concentration to a region of lower concentration is called _______

diffusion

Clostridium botulinum, which produces a toxin that causes botulism, is a major concern of the food industry due to its production of an extremely heat-resistant _________.

endospore Clostridium botulinum causes botulism, a food-borne disease that results from ingestion of botulinum toxin, the deadliest toxin known. In order to prevent botulism, food must be prepared and stored properly. The extreme heat resistance of C. botulinum endospores is a major concern of the food industry.

Most substances are able to undergo passive diffusion across the plasma membrane in order to enter a cell. (T/F)

false Most substances cannot freely diffuse across the cell membrane in order to enter a cell. Larger molecules, ions, and polar substances must enter the cell by the use of transport proteins.

Germination

germinant receptor proteins detect sugars or amino acids

Capsules and slime layers are networks of polysaccharides that can extend from the bacterial surface. Both capsules and slime layers can be encompassed by the general term _________.

glycocalyx The term glycocalyx refers to a layer consisting of a network of polysaccharides extending from the surface of the cell. The term can encompass both capsules and slime layers because they usually are composed of polysaccharides.

Some molecules needed for survival cannot be synthesized by the cell but instead must be obtained from the environment. These types of molecules include vitamins and amino acids and are collectively called ______ ______

growth factors Some microbes are unable to synthesize certain molecules needed for survival. These molecules are called growth factors, and they must be obtained from the environment. There are three types of growth factors: amino acids, purines and pyrimidines, and vitamins.

Activation

heat treatment prepares spores for germination

Nutrient uptake and diffusion of molecules into the bacterial cell become more efficient as the surface area-to-volume ratio ______

increases As the S/V ratio increases, the efficiency of nutrient uptake and molecule diffusion into the cell increases. There is more surface area compared to cell volume so there are more sites for nutrients and molecules to enter the cell.

Bacterial movement toward or away from a chemical is often described as a "random biased walk" due to the fact that ________

it still tumbles to change direction but it occurs less often than in the absence of a chemical, and runs more, creating an overall net motion in one direction

The plasma membrane must possess mechanisms for getting nutrients into the cell. Nutrients such as oxygen and hydrogen are needed in relatively large amounts and are referred to as ________

macroelements Macroelements or macronutrients are required in relatively large amounts. They are found in organic molecules such as proteins, lipids, nucleic acids, and carbohydrates.

In endospore formation, when DNA condenses and aligns itself in the center of the cell, the cell is called a(n) ______.

mother cell

Monotrichous

one flagellum extends from the cell to power locomotion Flagella arrangements can be used in taxonomy and reveals different microbial adaptations to environmental challenges.

The germination process of an endospore into a vegetative cell involves core enzymes becoming active due to increased water levels resulting in the ________ stage.

outgrowth Eventually water levels inside the germinating spore reach those of vegetative cells and enzymes in the core become active. This allows the outgrowth stage of germination and the spore begins synthesizing the various molecules it needs to a vegetative state.