Chapter Four Microbiology

how to identify streptococci

(a) Division in one plane produces diplococci and streptococci. (b) Division in two planes produces tetrads. (c) Division in three planes produces sarcinae, and (d) division in multiple planes produces staphylococci.

In the figure, which diagram of a cell wall contains teichoic acids?

A gram pos

Flagella

A long, whip-like filament that helps in cell motility. Many bacteria are flagellated, and sperm are flagellated. The long outermost region, the filament, is constant in diameter and contains the globular (roughly spherical) protein flagellin arranged in several chains that intertwine and form a helix around a hollow core. In most bacteria, filaments are not covered by a membrane or sheath, as in eukaryotic cells. The filament is attached to a slightly wider hook, consisting of a different protein. the flagella (and cilia) of eukaryotic cells are more complex than those of bacteria.

endospore

A thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions. thermophilic

atypical cell walls

Acid-fast cell walls Mycoplasmas (sterols in plasma membrane) Archaea (wall-less)

Which of these statements is true of plasmids? Plasmids often contain genes that give bacteria resistance to antibiotics. Plasmids are usually circular pieces of DNA. Plasmids can be passed from one bacterial cell to another via the pilus. This process is called conjugation. All of these statements are true.

All of these statements are true.

chemotaxis

Cell movement that occurs in response to chemical stimulus

Which of the following is NOT a structure of prokaryotic cells? Ribosome Flagellum Capsule Chloroplast Chromosome

Chloroplast Algae and green plants contain this unique organelle, a membrane-enclosed structure that contains both the pigment chlorophyll and the enzymes required for the light-gathering phases of photosynthesis.

Which of the following is NOT characteristic of the glycocalyx found in bacteria? Creates a slimy, slippery coating that prevents bacteria form attaching to surfaces A viscous coating surrounding the cell made of polysaccharide, polypeptide, or both A structure that can be visualized by negative staining If firmly attached, contributes to bacterial virulence

Creates a slimy, slippery coating that prevents bacteria form attaching to surfaces Slimy and slippery coating that prevents bacteria form attaching to surfaces would NOT be a characteristic of the bacterial glycocalyx. The bacterial glycocalyx is a viscous (sticky), gelatinous polymer that is external to the cell wall and composed of polysaccharide, polypeptide, or both. Its chemical composition varies widely with the species. For the most part, it is made inside the cell and secreted to the cell surface.

osmosis

Diffusion of water through a selectively permeable membrane from an area with a high concentration of water molecules to that with low concentration of water molecules

Which of the following statements is TRUE? Endospores are easily stained in a Gram stain. A cell can produce many endospores. Endospores allow a cell to survive environmental changes by producing a dormant period with no growth. A cell produces one endospore and keeps growing. Endospores are for reproduction.

Endospores allow a cell to survive environmental changes by producing a dormant period with no growth.

plasma membrane

Eukaryotic plasma membranes also contain carbohydrates and sterols, such as cholesterol. Because they lack sterols, prokaryotic plasma membranes are less rigid than eukaryotic membranes.

Structure of a prokaryotic cell

Fimbriae, ribosomes, cell wall, cell membrane, capsule, cytoplasmic matrix, flagellum, inclusion body, pilus, chromosome (dna), actin filaments, mesosome, slime layer

Which of the following bacterial structures is necessary for chemotaxis? Flagella Capsules Plasmids Metachromatic granules

Flagella Flagella are necessary for chemotaxis. Bacterial cells can alter the speed and direction of rotation of flagella and thus are capable of various patterns of motility, the ability of an organism to move by itself. One advantage of motility is that it enables a bacterium to move toward a favorable environment or away from an adverse one. The movement of a bacterium toward or away from a particular stimulus is called taxis, for example chemicals (chemotaxis).

Compare and contrast gram-positive and gram-negative cell walls with regard to (a) sensitivity to antimicrobial agents, (b) resistance to phagocytosis, (c) chemical composition, and(d) decolorization by alcohol.

Gram Positive Bacteria:- Many layers of peptidoglycan, forming a thick and very rigid structure.-Beribboned with teichoic acids : lipoteichoic ( linked to plasma membrane) and wall teichoic acid ( linked peptidoglycan layers).-Teichoic acids are negatively charged and play a role in cation movement in and out of the cell.Gram negative cell wall:-More complex than that of gram positive bacteria.Three layers:Inner membrane : ( plasma membrane) peptidoglycan, much thinner their in gram positive bacteria, only a few layers.Outer membrane, similar to inner membrane with some extras in addition to phospholipid bilayer.Periplasmic space, a space between the outer and inner membranes where the peptidoglycan is anchored by lipoproteins to the outer membrane. Involves transport as well.- It is toxic

You are observing a Gram stain of rod-shaped microorganisms that are linked in a chain and stain purple. How would you describe these bacteria using the correct terminology for the cell shape and arrangement? Gram-positive tetrads Gram-negative staphylococci Gram-positive coccobacilli Gram-positive streptobacilli

Gram-positive streptobacilli The best description for these cells would be gram-positive streptobacilli. During the Gram staining procedure, the application of alcohol dehydrated the peptidoglycan trapping the crystal violet-iodine complex in the thick cell wall imparting the purple color. The chainlike pattern would be best described with "strepto," the rod-shape of the cell would best be described with "bacilli," thus "streptobacilli."

You are observing a Gram stain of rod-shaped microorganisms that are linked in a chain and stain purple. How would you describe these bacteria using the correct terminology for the cell shape and arrangement? Gram-positive tetrads Gram-positive coccobacilli Gram-positive streptobacilli Gram-negative staphylococci

Gram-positive streptobacilli The best description for these cells would be gram-positive streptobacilli. During the Gram staining procedure, the application of alcohol dehydrated the peptidoglycan trapping the crystal violet-iodine complex in the thick cell wall imparting the purple color. The chainlike pattern would be best described with "strepto," the rod-shape of the cell would best be described with "bacilli," thus "streptobacilli."

Cilia

Hairlike projections that extend from the plasma membrane and are used for locomotion

Which of the following is NOT true of the gram-negative outer membrane? It contains enzymes for energy synthesis. It has polysaccharide antigens that are useful in bacterial identification. It contains lipids also known as endotoxins. It contains lipopolysaccharide. It is a part of the gram-negative cell wall.

It contains enzymes for energy synthesis. The outer membrane of the gram-negative cell consists of lipopolysaccharides (LPS), lipoproteins, and phospholipids. The outer membrane has several specialized functions. Its strong negative charge is an important factor in evading phagocytosis and the actions of complement (lyses cells and promotes phagocytosis), two components of the defenses of the host. The outer membrane also provides a barrier to detergents, heavy metals, bile salts, certain dyes, antibiotics (for example, penicillin), and digestive enzymes such as lysozyme. The plasma membranes, not the outer membrane, of bacteria contain enzymes capable of catalyzing the chemical reactions that break down nutrients and produce ATP.

Which has a cell wall prokaryotic or eukaryotic?

Many kinds of prokaryotes and eukaryotes contain a structure outside the cell membrane called the cell wall. With only a few exceptions, all prokaryotes have thick, rigid cell walls that give them their shape. Among the eukaryotes, some protists, and all fungi and plants, have cell walls.

taxis

Movement toward or away from a stimulus.

Which of the following is a likely outcome, based on the unique cell structure of members of the genus Mycoplasma? Mycoplasma species can release endotoxins when they lyse. Mycoplasma species usually stain gram-positive. Mycoplasma species are susceptible to disruption by lysozymes. Mycoplasma species are susceptible to penicillin. Mycoplasma species have very flexible cells that can pass through bacteriologic filters.

Mycoplasma species have very flexible cells that can pass through bacteriologic filters. Mycoplasma species have very flexible cells that can pass through bacteriologic filters. Members of the genus Mycoplasma and related organisms have no cell walls. They have very flexible cells that can pass through bacteriologic filters. Their plasma membranes are unique among bacteria in having lipids called sterols, which are thought to help protect them from lysis.

With a light microscope, which of the following would allow discrimination between eukaryotes and prokaryotes? Observation of the plasma membrane Observation of photosynthetic pigment Observation of the ribosomes Observation of flagella Observation of nuclei

Observation of nuclei With a light microscope, the observation of nuclei would allow for discrimination between eukaryotes and prokaryotes because prokaryotic cells lack membrane-enclosed organelles, such as a a nucleus.

simple diffusion (passive transport)

Passive movement from high to low consentration

effect of penicillin

Penicillin interferes with the final linking of the peptidoglycan rows by peptide cross-bridges As a result, the cell wall is greatly weakened and the cell undergoes lysis, destruction caused by rupture of the plasma membrane and the loss of cytoplasm.

Why is penicillin selectively toxic to bacterial cells but harmless to human cells? Human cells actively transport penicillin out of the cell. Penicillin is rapidly metabolized and destroyed by human cells. Penicillin is inactivated within lysosomes of human cells. The glycocalyx of an animal cell provides a barrier through which penicillin cannot pass. Penicillin specifically weakens peptidoglycan, which is found only in bacterial cells.

Penicillin specifically weakens peptidoglycan, which is found only in bacterial cells. Penicillin specifically weakens peptidoglycan, which is found only in bacterial cells. Certain antibiotics, such as penicillin, destroy bacteria by interfering with the formation of the peptide cross bridges of peptidoglycan, thus preventing the formation of a functional cell wall. Human cells do not have cell walls and do not contain peptidoglycan, thus rendering penicillin harmless to them.

How do spirochetes and spirilla differ? Spirochetes and spirilla are basically the same organisms and the terms can be used interchangeably. Spirochetes do not have a cell wall but spirilla do. Spirilla are found in chains of cells whereas spirochetes exist as individual cells. Spirilla have an external flagella but spirochetes have axial filaments. Spirochetes have a rigid, corkscrew shape while spirilla are helical and more flexible.

Spirilla have an external flagella but spirochetes have axial filaments.

axial filaments

Spirochetes move by means of axial filaments, or endoflagella, bundles of fibrils that arise at the ends of the cell beneath an outer sheath and spiral around the cel

structure of bacterial cell wall

The bacterial cell wall is composed of a macromolecular network called peptidoglycan (also known as murein), which is present either alone or in combination with other substances. Peptidoglycan consists of a repeating disaccharide connected by polypeptides to form a lattice that surrounds and protects the entire cell. The disaccharide portion is made up of monosaccharides called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) (from murus, meaning wall), which are related to glucose.

Which of the following is NOT a function of the capsule? The capsule can serve as a source of nutrition for the bacterial cell when nutrients are scarce. The capsule protects the bacteria from phagocytocysis. The capsule can aid the bacterium in attaching to a surface. The capsule regulates what enters and leaves the cell.

The capsule regulates what enters and leaves the cell.

What statement most accurately describes the structure of the plasma membrane?

The plasma membrane is a phospholipid bilayer with the hydrophilic phosphate groups oriented toward the inside and outside of the cell.

Sporulation/Sporogenesis

The process of endospore formation within a vegetative cell takes several hours

Which of the following statements is INCORRECT regarding prokaryotic cells? They lack membrane-enclosed organelles. Their DNA is not enclosed within a membrane. They lack a plasma membrane. They reproduce by binary fission. They typically have a circular chromosome.

They lack a plasma membrane.

Gram positive cell wall

Thick peptidoglycan Teichoic acids

gram negative cell wall

Thin peptidoglycan Outer membrane Periplasmic space endotoxin outer membrane: lipopolysaccharide LPS

The cell walls of bacteria are responsible for the shape of the bacteria and the difference in the Gram stain reaction. True False

True

serovars

Variations within a species of gram-negative bacteria

acid fast cell walls

Waxy lipid (mycolic acid) bound to peptidoglycan can be stained with carbolfuchsin

Which drawing in the figure possesses an axial filament? a b c d e

a

extracellular polymeric substance (EPS)

a glycocalyx that helps cells in a biofilm attach to their target environment and to each other

Antigen

a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

Mycoplasma

among prokaryotes, certain types of cells have no walls or have very little wall material.

Archaella

archaeal cells have archaella (singular: archaellum). Archaella share similarities with bacterial flagella and pili

Which drawing in the figure is a tetrad? a b c d e

b

Functions of the glycocalyx include all of the following EXCEPT protection against dehydration. increased virulence. biofilm formation. binary fission. source of nutrition.

binary fission.

In the figure, which diagram of a cell wall has a structure that protects against osmotic lysis?

both

Fimbriae

can occur at the poles of the bacterial cell or can be evenly distributed over the entire surface of the cell. They can number anywhere from a few to several hundred per cell. Fimbriae have a tendency to adhere to each other and to surfaces. As a result, they are involved in forming biofilms and other aggregations on the surfaces of liquids, glass, and rocks. Fimbriae can also help bacteria adhere to epithelial surfaces in the body

Which structure acts like an "invisibility cloak" and protects bacteria from being phagocytized? slime layer cell membrane capsule cell wall fimbriae

capsule

Penicillin inhibits

cell wall synthesis

Which drawing in the figure is streptococci? a b c d e

d

Which of the following is NOT true of the gram-negative outer membrane? It contains enzymes for energy synthesis. It has polysaccharide antigens that are useful in bacterial identification. It contains lipopolysaccharide. It contains lipids also known as endotoxins. It is a part of the gram-negative cell wall.

does NOT contain enzymes for energy synthesis. The outer membrane of the gram-negative cell consists of lipopolysaccharides (LPS), lipoproteins, and phospholipids. The outer membrane has several specialized functions. Its strong negative charge is an important factor in evading phagocytosis and the actions of complement (lyses cells and promotes phagocytosis), two components of the defenses of the host. The outer membrane also provides a barrier to detergents, heavy metals, bile salts, certain dyes, antibiotics (for example, penicillin), and digestive enzymes such as lysozyme. The plasma membranes, not the outer membrane, of bacteria contain enzymes capable of catalyzing the chemical reactions that break down nutrients and produce ATP.

Which of the following is NOT a functionally analogous pair? A) chloroplasts - thylakoids B) mitochondria - prokaryotic plasma membrane C) 9+2 flagella - bacterial flagella D) nucleus -nucleiod region E) cilia - pili

e) cilia - pili

Spirochetes and spirilla are both spiral-shaped bacteria. However, they differ in that spirochetes have __________ and spirilla do not. endoflagella peritrichous flagella fimbriae N-acetylglucosamine

endoflagella The major difference between spirochetes and spirilla is the presence of endoflagella. Spirochetes move by means of axial filaments, or endoflagella, bundles of fibrils that arise at the ends of the cell beneath an outer sheath and spiral around the cell.

eukaryotic cells do not contain

endospore returns to its vegetative state by a process

Germination

endospore returns to its vegetative state by a process of germination triggered by high heat, canning, or by germinants

damage to cell wall

exposure to lysozyme

The structure of the prokaryotic cell that allows it to move with direction is called

flagellum

gas vacuoles

found in aquatic, photosynthetic bacteria and archaea provide buoyancy in gas vesicles

Which one of the following organisms has a cell wall? L forms animal cells fungi protoplasts mycoplasmas

fungi

In the figure, which diagram of a cell wall possesses lipid A/endotoxin responsible for symptoms associated with infection?

gram neg

Cell wall that has porins, O lipopolysaccharide, and lipid A

gram neg cell wall

In the figure, which diagram of a cell wall is resistant to many antibiotics (e.g., penicillin)?

gram negative

cell wall that has teichoic acid

gram pos

fimbriae and pili

hairlike appendages that are shorter, straighter, and thinner than flagella. These structures, which consist of a protein called pilin arranged helically around a central core, are divided into two types, fimbriae and pili, having very different functions

monomorphic

having a single form

LPS

lipopolysaccharide large, complex molecule that contains lipids and carbohydrates and consists of three components: (1) lipid A, (2) a core polysaccharide, and (3) an O polysaccharide. Lipid A is the lipid portion of the LPS and is embedded in the top layer of the outer membrane. When gram-negative bacteria die, they release lipid A, which functions as an endotoxin. Lipid A is responsible for the symptoms associated with infections by gram-negative bacteria, such as fever, dilation of blood vessels, shock, and blood clotting. The core polysaccharide is attached to lipid A and contains unusual sugars. Its role is structural—to provide stability. The O polysaccharide extends outward from the core polysaccharide and is composed of sugar molecules. The O polysaccharide functions as an antigen and is useful for distinguishing serovars of gram-negative bacteria.

polypeptide

long chain of amino acids that makes proteins

Which of the following terms best describes the cell in the figure? lophotrichous flagella amphitrichous flagella peritrichous flagella monotrichous flagellum axial filament

lophotrichous flagella

Which organelle would play the most direct role in eliminating bacteria engulfed by a phagocytic white blood cell?

lysosome

pleomorphic

many shapes

types of flagella

monotrichous- polar, single flagella at one pole amphitrichous - flagella at both poles lophotrichous- tuft of flagella coming from one pole peritrichous - distributed over the entire cell H antigen is useful for distinguishing among serovars, or variations within a species, of gram-negative bacteria (see page 304). For example, there are at least 50 different H antigens for E. coli. Those serovars identified as E. coli O157:H7 are associated with foodborne epidemics.

Chemotaxis refers to the ability of microorganisms to __________. move in a wavelike motion escape phagocytosis attach to solid surfaces move toward or away from chemical stimuli survive under adverse conditions

move toward or away from chemical stimuli Chemotaxis refers to the ability of microorganisms to move toward or away from chemical stimuli. The movement of a bacterium toward or away from a particular stimulus is called taxis. Such stimuli include chemicals (chemotaxis) and light (phototaxis). Motile bacteria contain receptors in various locations. These receptors pick up chemical stimuli, such as oxygen, ribose, and galactose. In response to the stimuli, information is passed to the flagella. If the chemotactic signal is positive, called an attractant, the bacteria move toward the stimulus with many runs and few tumbles. If the chemotactic signal is negative, called a repellent, the frequency of tumbles increases as the bacteria move away from the stimulus.

phototaxis

movement in response to light

The term describing bacteria with flagella distributed over the entire surface of the cell is __________. monotrichous lophotrichous peritrichous amphytrichous

peritrichous Some prokaryotic cells have flagella, which are long filamentous appendages that propel bacteria. The term describing bacteria with flagella distributed over the entire surface of the cell is peritrichous. Flagella may also be monotrichous (a single flagellum at one pole); lophotrichous (a tuft of flagella coming from one pole); or amphitrichous (flagella at both poles of the cell).

Chromatophores/Thylakoids

photosynthesis pigment cells that change the color of an organism, allowing it to camouflage

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

In a prokaryotic cell, all of the following are functions of either fimbriae or pili EXCEPT __________. attachment to a surface protection from phagocytosis formation of biofilms transfer of DNA

protection from phagocytosis Fimbriae and pili do NOT function in protection from phagocytosis. Fimbriae help cells adhere to surfaces and are involved in forming biofilms. Pili are commonly involved in DNA transfer and twitching or gliding motility.

Carbohydrates that make up the cell wall

pseudopeptidoglycan and peptidoglycan

lysozyme

removes the cell wall

Inclusions (prokaryotes)

reserve deposits that accumulate certain nutrients

Gram-negative cells contain a periplasmic space that is __________. the site of protein synthesis filled with lysozyme rich in degradative enzymes abundant in teichoic acid a site of endocytosis

rich in degradative enzymes In Gram-negative cells, the peptidoglycan is bonded to lipoproteins in the outer membrane and is in the periplasm, a gel-like fluid in its periplasmic space, the region between the outer membrane and the plasma membrane. The periplasm is rich in degradative enzymes and transport proteins.

Glycocalyx

secretion on the surface of prokaryotes forms this a capsule made up of a fuzzy coat of sticky/viscous sugars slime layer polysaccharide/polipeptide layer presence is determined by negative staining

Consider a gram-positive cell in a hypertonic medium. If the peptidoglycan were damaged, the cell would __________.

shrink

repellent

signal is negative; frequency of tumbles increases as the bacteria move away from the stimulus.

attractant

signal is positive, called an attractant, the bacteria move toward the stimulus with many runs and few tumbles

ribosomes

site of protein synthesis 70S-pro 80S-euk

Which of the following pairs is matched correctly? spheroplast—gram-negative bacteria that are exposed to lysozyme but retain some of the outer membrane protoplast—a genus of bacteria that typically do not have cell walls Mycoplasma spp.—bacteria that spontaneously, or in response to penicillin or lysozyme, partially lose their cell walls and swell into irregularly shaped bacteria that divide and metabolize and may regain their cell wall L form—a wall-less bacterium created by the action of lysozyme; the plasma membrane remains intact, and the cell carries on metabolism

spheroplast—gram-negative bacteria that are exposed to lysozyme but retain some of the outer membrane The following are matched correctly: spheroplast—gram-negative bacteria that are exposed to lysozyme but retain some of the outer membrane. When lysozyme is applied to gram-negative cells, usually the wall is not destroyed to the same extent as in gram-positive cells; some of the outer membrane also remains. In this case, the cellular contents, plasma membrane, and remaining outer wall layer are called a spheroplast.

purpose of glycocalyx

strengthens the cell surface, helps attach cells together, and may contribute to cell-cell recognition capsule may prevent it from being destroyed by phagocytosis.

Spherical bacteria that divide and remain attached in chainlike patterns are called __________. staphylococci streptococci tetrads spirochetes

streptococci

Spherical bacteria that divide and remain attached in chainlike patterns are called __________. tetrads streptococci staphylococci spirochetes

streptococci

Osmotic lysis

swelling and bursting of a cell in a hypotonic solution

Where are phospholipids most likely found in a eukaryotic cell?

the plasma membrane and organelles

Cells placed in a hypertonic solution tend to lose water due to osmotic pressure. t/f

true

If you observe rod-shaped red cells after the Gram stain, you can assume their cell walls contain endotoxin.

true

endocytosis and exocytosis

types of active transport

Pili

usually longer than fimbriae and number only one or two per cell. Pili are involved in motility and DNA transfer. In one type of motility, called twitching motility, a pilus extends by the addition of subunits of pilin, makes contact with a surface or another cell, and then retracts (powerstroke) as the pilin subunits are disassembled. This is called the grappling hook model of twitching motility and results in short, jerky, intermittent movements. Some pili are used to bring bacteria together, allowing the transfer of DNA from one cell to another, a process called conjugation. Such pili are called conjugation (sex) pili

metachromatic granules

volutin phosphate reserves

protoplast

wall-less