Bacteriology Flashcards

Questions and Answers

Name some bacteria that display α, β, and γ hemolysis.

α Hemolysis: Streptococcus pneumoniae, Streptococcus viridans, some enterococci; β Hemolysis: Streptococcus pyogenes, Streptococcus agalactiae, S.aureus, Listeria monocytogenes; γ Hemolysis: some enterococci.

Name the bacteria associated with Group A Lancefield antigens.

S.pyogenes

Name the bacteria associated with Group B Lancefield antigens.

S.agalactiae

Name the bacteria associated with Group D Lancefield antigens.

Streptococcus bovis and enterococci (Enterococcus faecalis and Enterococcus faecium) Signup and view all the answers

Which Group D bacteria, Streptococcus or Enterococcus, can grow in hypertonic (6.5%) saline?

Enterococci can grow in hypertonic saline and S.bovis cannot. Signup and view all the answers

What tests can differentiate S.pneumoniae from S.viridans?

Optochin sensitivity, bile solubility, and quellung test Signup and view all the answers

What test can differentiate S.pyogenes and S.agalactiae?

Bacitracin sensitivity Signup and view all the answers

What are the clinically relevant gram-positive bacilli?

Corynebacterium, Listeria, Bacillus, and Clostridium. Signup and view all the answers

Which gram-positive bacillus has metachromatic granules?

Corynebacterium diphtheriae. Signup and view all the answers

What are the three major components of the bacterial envelope?

Capsule, cell wall, cell membrane Signup and view all the answers

Bacterial capsules are typically made from what macromolecule?

Polysaccharides Signup and view all the answers

What are the two notable examples of bacterial capsules made from a macromolecule other than polysaccharides?

Capsule of Bacillus anthracis is made from D-glutamic acid polypeptide; capsule of Yersinia pestis is made from amino acids. Signup and view all the answers

What are the two functions of a bacterial capsule?

Protect bacteria from phagocytosis and aid in attaching to host surfaces. Signup and view all the answers

What test allows identification of a capsule in bacteria?

The quellung test. Signup and view all the answers

Why are capsules an important target for medical therapy?

Capsules can be used for vaccine development. Signup and view all the answers

Bacterial cell walls are made from what macromolecule?

Peptidoglycan murein. Signup and view all the answers

What is the major function of the cell wall?

Protect bacteria against mechanical forces. Signup and view all the answers

What is Gram staining?

A procedure to classify bacteria by their cell wall's ability to absorb dyes. Signup and view all the answers

What color are gram-positive bacteria?

Blue. Signup and view all the answers

What color are gram-negative bacteria?

Pink. Signup and view all the answers

How do the peptidoglycan layers of gram-positive bacteria differ from those of gram-negative bacteria?

Gram-positive have thicker peptidoglycan walls; gram-negative have thinner walls with a periplasmic space. Signup and view all the answers

What important enzyme is found in the periplasmic space of gram-negative bacteria?

β-Lactamase. Signup and view all the answers

How do penicillins and cephalosporins work?

They bind to transpeptidase enzymes and prevent cross-linking in peptidoglycan. Signup and view all the answers

Which type of Gram-staining bacteria has teichoic and lipoteichoic acid?

Gram-positive bacteria. Signup and view all the answers

What are some of the pathologic effects of teichoic acid and LPS?

Induce cytokines that activate inflammatory pathways, leading to septic shock. Signup and view all the answers

What are the three components of LPS?

Outer polysaccharide (O-antigen), middle core polysaccharide, inner lipid A. Signup and view all the answers

What is the only gram-positive organism that has endotoxin?

Listeria monocytogenes. Signup and view all the answers

How do the cell walls of Mycobacteria species differ from those of gram-positive and gram-negative organisms?

Mycobacteria contain mycolic acids and do not Gram stain; they are acid-fast. Signup and view all the answers

What bacteria lack a cell wall?

Mycoplasma species. Signup and view all the answers

How do bacterial cell membranes differ from mammalian cell membranes?

Bacterial cell membranes lack sterols, except for Mycoplasma species. Signup and view all the answers

Where is the electron transport chain located in bacteria?

Bacterial cell membrane. Signup and view all the answers

What stimulus drives the direction of motion of flagellated bacteria?

Chemical gradients (chemotaxis). Signup and view all the answers

Name two bacteria with a single polar flagellum.

Vibrio cholerae, Campylobacter jejuni. Signup and view all the answers

What two bacteria have multiple flagella?

Escherichia coli, Proteus mirabilis. Signup and view all the answers

What are the two types of pili and what are their functions?

Common pili (fimbriae) mediate bacterial adhesion; sex pili allow for exchange of genetic material. Signup and view all the answers

Glycocalyx, which allows bacteria to adhere to surfaces, is made of what macromolecule?

Polysaccharides. Signup and view all the answers

Name some pathogenic bacteria that utilize a slime layer glycocalyx for infection.

Streptococcus mutans, Streptococcus sanguis, Staphylococcus epidermidis. Signup and view all the answers

What metabolically inactive structure formed by certain bacteria is resistant to environmental stresses?

Spore. Signup and view all the answers

What advantage does spore formation offer bacteria?

Ensures survival in harsh environments. Signup and view all the answers

What are the contents of an endospore?

Bacterial DNA, sparse cytoplasm, cell membrane, peptidoglycan, thick keratin-like coat. Signup and view all the answers

What are the two important spore-forming gram-positive rods?

Bacillus, Clostridium. Signup and view all the answers

Why are antibiotics not effective against spores?

Antibiotics cannot penetrate the spore coat and can't act on inactive spores. Signup and view all the answers

What is a fomite?

An inanimate object that can harbor and spread infections. Signup and view all the answers

What are the four phases of bacterial growth?

Lag phase, logarithmic phase, stationary phase, death phase. Signup and view all the answers

During what phase do bacteria have the highest metabolic activity but without cell division?

Lag phase. Signup and view all the answers

During what phase is growth the fastest?

Log phase. Signup and view all the answers

During what phase do β-lactam drugs act?

Log phase. Signup and view all the answers

In what phase does bacterial growth equal that of bacterial death?

Stationary phase. Signup and view all the answers

During what phase do spores form?

Stationary phase. Signup and view all the answers

During what phase have nutrient sources been exhausted?

Death phase. Signup and view all the answers

How are bacteria groups separated according to their oxygen requirements?

Obligate aerobes, facultative anaerobes, microaerophilic, aerotolerant anaerobes, obligate anaerobes. Signup and view all the answers

What are some obligate aerobe bacteria?

Nocardia, Bacillus, Neisseria, Pseudomonas, Bordetella, Legionella, Brucella. Signup and view all the answers

What are some obligate anaerobic bacteria?

Clostridium, Actinomyces, Bacteroides. Signup and view all the answers

Why do obligate aerobes require oxygen?

Their metabolism requires oxygen as the final electron acceptor. Signup and view all the answers

How are facultative anaerobes different from obligate aerobes?

Facultative anaerobes can grow without oxygen using fermentation. Signup and view all the answers

How do microaerophilic bacteria generate adenosine triphosphate (ATP)?

Only through fermentation. Signup and view all the answers

How do microaerophilic bacteria tolerate low levels of oxygen?

They have superoxide dismutase, but no catalase. Signup and view all the answers

Why are obligate anaerobes unable to grow in the presence of oxygen?

They lack enzymes to protect against free O2 radicals. Signup and view all the answers

What are obligate intracellular organisms?

Organisms that can only survive within host cells. Signup and view all the answers

How do obligate intracellular organisms generate ATP?

They utilize the ATP of a host cell. Signup and view all the answers

What are facultative intracellular organisms?

Organisms that can survive both intracellularly and extracellularly. Signup and view all the answers

What are some facultative intracellular organisms?

Brucella, Salmonella typhi, Francisella tularensis, Legionella, Mycobacterium, Yersinia, Listeria monocytogenes. Signup and view all the answers

By what process do bacteria multiply?

Binary fission. Signup and view all the answers

Are bacteria haploid?

True Signup and view all the answers

Name two types of DNA forms found in bacteria.

Chromosomal DNA, plasmid DNA. Signup and view all the answers

Name the location of chromosomal DNA in bacteria.

Nucleoid. Signup and view all the answers

Describe the DNA structure of plasmids.

Double-stranded circular DNA. Signup and view all the answers

Name some genes carried on plasmids.

Antibiotic resistance genes, pili genes, exotoxin genes. Signup and view all the answers

How are plasmids transferred between bacteria?

Conjugation. Signup and view all the answers

What are the size and subunits for bacterial and eukaryotic ribosomes?

Bacterial: 70S; Eukaryotic: 80S. Signup and view all the answers

Name four ways in which bacteria are able to acquire new genetic information.

Transformation, transduction, conjugation, transposon insertion. Signup and view all the answers

How do bacteria acquire genetic information via transformation?

Bacteria take up DNA from the environment. Signup and view all the answers

What is a bacterium that is able to utilize transformation?

Competent recipient bacterium. Signup and view all the answers

What mediates the transfer of genetic material in transduction?

Bacteriophages (phages). Signup and view all the answers

How do bacteriophages normally reproduce?

By injecting bacteria with their phage DNA. Signup and view all the answers

How do bacteriophages transfer bacterial genetic material via transduction?

Newly produced phages are packaged with bacterial genes. Signup and view all the answers

What are the two types of phages?

Virulent phage, temperate phage. Signup and view all the answers

Which type of phage causes near-immediate lysis of bacteria?

Virulent phage. Signup and view all the answers

What is the name of the incorporated phage DNA in a temperate phage?

Prophage. Signup and view all the answers

Name the two types of transduction and the type of phage responsible for each.

Generalized (virulent phage), specialized (temperate phage). Signup and view all the answers

What part of the bacterial chromosome is transferred in generalized transduction?

Any part of the bacterial genome. Signup and view all the answers

What part of the bacterial chromosome is transferred in specialized transduction?

The segment adjacent to the prophage. Signup and view all the answers

Name some bacterial toxins acquired through specialized transduction.

Diphtheria toxin, botulinum toxin, cholera toxin. Signup and view all the answers

What types of DNA can be exchanged by conjugation?

Both chromosomal and plasmid. Signup and view all the answers

What plasmid encodes the proteins needed to form the sex pilus?

The F plasmid. Signup and view all the answers

What is the term given when the F plasmid incorporates into the bacterial chromosomal DNA?

Hfr (high-frequency recombination). Signup and view all the answers

Why are transposons medically relevant?

Transposons aid in the spread of antibiotic resistance. Signup and view all the answers

Name a notable example of transposon-mediated drug resistance.

The vanA transposon. Signup and view all the answers

What two bacteria undergo programmed rearrangement of surface antigens?

Neisseria gonorrhoeae, Borrelia recurrentis. Signup and view all the answers

What are the basic shape classifications of bacteria?

Cocci, bacilli, and spirochetes. Signup and view all the answers

What are the different pattern arrangements of cocci and common examples of each?

Diplococci (Neisseria), chains (streptococci), clusters (staphylococci). Signup and view all the answers

What are the two main gram-positive cocci bacteria?

Streptococcus (catalase negative), Staphylococcus (catalase positive). Signup and view all the answers

Study Notes

Bacterial Envelope Components

Major components include capsule, cell wall, and cell membrane.

Bacterial Capsules

Typically composed of polysaccharides, which are sugar-based macromolecules.
Exception: Bacillus anthracis has a capsule made from D-glutamic acid polypeptide, and Yersinia pestis has a capsule made from amino acids.

Functions of Bacterial Capsules

Serve as virulence factors that protect against phagocytosis by immune cells.
Facilitate attachment to host tissues.

Capsule Identification

The quellung test uses anti-capsular antibodies to visualize capsular swelling under light microscopy.

Medical Relevance of Capsules

Capsules contain polysaccharides essential for developing vaccines, such as those for S. pneumoniae and H. influenzae type B.

Bacterial Cell Walls

Comprised of peptidoglycan (murein), a polymer of sugars and amino acids.
Major function: provides rigidity and protects against osmotic pressure.

Gram Staining

A classification method based on cell wall's ability to absorb crystal violet dye, followed by a counterstain.
Gram-positive bacteria appear blue; gram-negative bacteria appear pink.

Peptidoglycan Layers

Gram-positive bacteria have thicker layers (up to 90% of dry weight) than gram-negative bacteria (around 10% of dry weight) which also have a periplasmic space.

Key Enzymes

β-Lactamase is found in the periplasmic space of gram-negative bacteria and confers resistance to certain antibiotics.

Antibiotics Targeting Cell Walls

Penicillins and cephalosporins target transpeptidase enzymes, preventing peptidoglycan cross-linking.

Cell Wall Characteristics

Gram-positive bacteria possess teichoic and lipoteichoic acids; gram-negative bacteria have lipopolysaccharides (LPS).

Pathological Effects

Teichoic acid and LPS can induce cytokine production leading to septic shock and disseminated intravascular coagulation (DIC).

Components of Lipopolysaccharides (LPS)

Composed of an outer polysaccharide (O-antigen), a middle core polysaccharide, and an inner lipid A that elicits toxic effects.

Unique Endotoxin

Listeria monocytogenes is the only gram-positive organism that possesses an endotoxin.

Mycobacteria’s Cell Walls

Contain mycolic acids, making them acid-fast and resistant to standard Gram staining techniques.

Non-Gram Staining Bacteria

Various bacteria rely on alternative staining methods such as dark-field microscopy, Giemsa stain, and Ziehl-Neelsen stain.

Cell Wall-less Bacteria

Mycoplasma species lack a cell wall.

Bacterial Cell Membranes

Unique in that they do not contain sterols except in Mycoplasma species.

Location of Electron Transport Chain

Found within the bacterial cell membrane instead of membranous organelles like mitochondria.

Bacterial Motion

Flagella allow movement, guided by chemical gradients (chemotaxis).

Bacterial Flagella Types

Single polar flagellum in Vibrio cholerae and Campylobacter jejuni; multiple flagella in Escherichia coli and Proteus mirabilis.

Pili Functions

Common pili (fimbriae) assist in adhesion; sex pili facilitate genetic material exchange.

Glycocalyx Composition

Made of polysaccharides; tightly associated glycocalyx is a capsule, while loosely associated is a slime layer.

Slime Layer Pathogens

Pathogens like Streptococcus mutans and Staphylococcus epidermidis use slime layers to adhere in their respective environments.

Spores

Metabolically inactive structures that help bacteria endure environmental stresses; require autoclaving for sterilization due to heat, chemical, and radiation resistance.

Endospore Contents

Composed of bacterial DNA, sparse cytoplasm, a cell membrane, peptidoglycan, and a protective keratin-like coat.

Clinical Relevance of Spores

Antibiotics are ineffective against spores due to their impermeable coats and inactivity.

Fomites

Inanimate objects that can harbor and transmit infections (e.g., contaminated hospital surfaces).

Bacterial Growth Phases

Consist of lag, logarithmic, stationary, and death phases; each has distinct metabolic activities and growth dynamics.

Bacterial Oxygen Requirements

Classified as obligate aerobes, facultative anaerobes, microaerophilic, aerotolerant anaerobes, and obligate anaerobes based on oxygen utilization.

Aerotolerant Organisms

Can survive in both oxygen-rich and anaerobic environments but only metabolize anaerobically.

Intracellular Bacteria

Obligate intracellular organisms (e.g., Chlamydia, Rickettsia) depend on host cells for ATP, while facultative intracellular organisms can exist both inside and outside host cells.

Bacterial Multiplication

Occurs via binary fission, and bacteria are haploid.

Bacterial DNA Forms

Contain chromosomal DNA (in nucleoid) and plasmid DNA (circular, double-stranded).

Gene Transfer Mechanisms

Include transformation, transduction, conjugation, and transposon insertion.

Transformation Process

Involves uptake of free DNA from the environment by competent bacteria.

Bacteriophage Function

Mediate gene transfer through transduction by infecting bacteria and packaging bacterial DNA into new phages.

Types of Transduction

Generalized transduction (virulent phage) transfers any part of the bacterial genome; specialized transduction (temperate phage) transfers specific adjacent segments.

Toxins from Specialized Transduction

Includes diphtheria toxin and cholera toxin, highlighting the exchange of genetic factors.

Conjugation and Plasmids

The F plasmid facilitates the formation of sex pili for genetic exchange, leading to Hfr strains when integrated into the bacterial genome.

Medical Implications of Transposons

They contribute to antibiotic resistance spread, illustrated by the vanA transposon linked to vancomycin resistance.

Antigenic Variation

Organisms like Neisseria gonorrhoeae undergo programmed rearrangements to evade the immune system.

Bacterial Shape Classifications

Bacteria are categorized into cocci, bacilli, and spirochetes based on their shapes.

Cocci Arrangements

Examples include diplococci (e.g., Neisseria), chains (e.g., streptococci), and clusters (e.g., staphylococci).

Gram-Positive Cocci Differentiation

Streptococcus species are catalase negative, while Staphylococcus are catalase positive; tests can differentiate between them.

Clinical Identification Tests

Utilize selective media like sheep blood agar and additional biochemical tests (e.g., coagulase, bacitracin sensitivity) to identify specific bacterial species.

Lancefield Classification

Group A (S. pyogenes), B (S. agalactiae), and D (Streptococcus bovis and enterococci) are classified based on carbohydrate antigens in their cell walls.

Enterococci Characteristics

Enterococcus faecalis can grow in hypertonic saline while S. bovis cannot, highlighting a key distinction in the group.

Differentiation of Streptococcus Species

Tests like the optochin sensitivity and bacitracin sensitivity are vital for identifying specific Streptococcus species, linking back to their clinical relevance.

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Description

Test your knowledge on the bacterial envelope components, the composition of bacterial capsules, and specific examples of capsules. This quiz includes key concepts in bacteriology and helps reinforce essential microbiology terms.