Bacterial Cell Structure, Physiology, Metabolism, and Genetics

Flashcards covering bacterial cell structure, physiology, microbial diversity, staining procedures, media types, growth kinetics, metabolic pathways, and genetics.

How is an ecological niche distinguished from a habitat in microbial ecology?

A niche is the place or location where an organism resides, whereas a habitat is the specific location of the organism where its essential resources are found.

What are the primary duties of a clinical microbiologist?

The primary duties are to isolate, identify, and analyze disease-causing bacteria (pathogens).

Which modern molecular techniques have shifted bacterial identification away from traditional biochemical testing?

Nucleic acid amplification, nucleic acid sequencing, and MALDI-TOF mass spectrometry (matrix-assisted laser desorption/ionization--time-of-flight).

Why is Anton van Leeuwenhoek referred to as the 'father of protozoology and bacteriology'?

He earned this title for discovering 'wee beasties' and 'animalcules' using his homemade microscopes.

How are protozoa categorized based on their structures for locomotion?

They are categorized by flagella (whip-like), pseudopodia (false feet), or cilia (eyelash).

How do dimorphic fungi alter their structural growth form based on environmental temperature?

They grow as unicellular yeast at human body temperature ($37^\text{o}\text{C}$) and as filamentous molds at room temperature ($22^\text{o}\text{C}$).

What is a cytopathic effect, and what visible changes indicate its presence in laboratory cell lines?

It refers to visible diagnostic changes in cell lines, such as inclusions, cell rounding, and syncytium formation.

What is the difference between a virion and a bacteriophage?

A virion is a complete virus particle outside a host cell, while a bacteriophage is a virus that specifically infects and destroys bacterial cells.

How do prokaryotic and eukaryotic cells compare regarding ribosome structure?

Prokaryotes possess $70\text{S}$ ribosomes (composed of $50\text{S}$ and $30\text{S}$ subunits), whereas eukaryotes possess $80\text{S}$ ribosomes (composed of $60\text{S}$ and $40\text{S}$ subunits).

What are the typical dimensions of prokaryotic cells compared to eukaryotic cells?

Prokaryotes typically measure 0.4\text{--}2\text{ }\text{̠m} in diameter and 0.5\text{--}5\text{ }\text{̠m} in length, while eukaryotes measure 10\text{--}100\text{ }\text{̠m} in diameter and >10\text{ }\text{̠m} in length.

Where does electron transport occur in prokaryotic cells versus eukaryotic cells?

In prokaryotes, electron transport occurs in the plasma membrane; in eukaryotes, it occurs in the inner membrane of mitochondria and chloroplasts.

What distinct features characterize organisms belonging to the domain Archaea?

They are unicellular prokaryotes closely related to eukaryotes that lack peptidoglycan in their cell walls and include extremophiles such as halophiles, thermophiles, and methanogens.

How do serovar and biovar sub-species designations differ?

A serovar is distinguished by antigenic differences, whereas a biovar is distinguished by biochemical differences.

What structural features characterize bacterial endospores and how are they visualized in the Schaeffer-Fulton stain?

Endospores are dormant, highly resistant structures produced by Bacillus and Clostridium; in the Schaeffer-Fulton stain using malachite green and safranin counterstain, endospores appear green inside pink/red bacterial cells.

What distinctive morphological appearance do Clostridium tetani endospores exhibit?

They display terminal spores that give them a 'tennis racquet' or 'lollipop' appearance.

What are the primary chemical constituents of the Gram-positive bacterial cell wall?

A thick layer of peptidoglycan composed of alternating NAG and NAM chains linked by peptide bridges, containing teichoic acid and lipoteichoic acid.

What are the three structural regions of Lipopolysaccharide (LPS) found in Gram-negative bacteria?

O-specific polysaccharide (antigenic), core polysaccharide, and Lipid A (endotoxin causing fever and shock).

What cell wall constituent accounts for approximately $600\text{--}601\text{--}60\text{\%}$ of lipids in acid-fast bacteria?

Mycolic acid, found in genera such as Mycobacterium and Nocardia.

Which bacterial genera naturally lack a cell wall and contain sterols in their plasma membrane?

Mycoplasma, Ureaplasma, and Acholeplasma.

What are the four recognized arrangements of bacterial flagella?

Monotrichous (single flagellum at one end), Lophotrichous (tuft of flagella at one end), Amphitrichous (flagella at both ends), and Peritrichous (flagella surrounding the entire organism).

What is the largest known bacterium and what size does it reach?

Thiomargarita namibiensis, which reaches a size of $0.1\text{--}0.3\text{ mm}$.

What are the four sequential steps and reagents used in the Gram stain procedure?

1. Primary stain: Crystal violet (1 minute); 2. Mordant: Gram's iodine (1 minute); 3. Decolorizer: Alcohol or alcohol-acetone (quick rinse); 4. Counterstain: Safranin (30 seconds).

How do Acridine Orange and Calcofluor White function as differential fluorochrome dyes?

Acridine Orange stains nucleic acids in both live and dead bacteria bright orange; Calcofluor White binds to chitin in fungal cell walls, fluorescing bright apple-green or blue-white.

What purpose does methylene blue serve when staining Corynebacterium diphtheriae?

It is used to observe metachromatic granules.

What are the primary elemental components required for bacterial growth and their relative dry weight percentages?

Carbon ($50\text{\%}$ dry weight), Nitrogen ($14\text{\%}$), and Phosphorus/Sulfur ($4\text{\%}$).

How are enriched, selective, and differential media defined in clinical microbiology?

Enriched media contains extra nutrients for fastidious organisms; Selective media contains inhibitors to select for specific bacteria; Differential media visualizes metabolic differences between bacteria.

How do psychrophiles, mesophiles, and thermophiles differ in temperature preferences?

Psychrophiles grow best at cold temperatures (10\text{^\text{o}C}\text{--}20\text{^\text{o}C}), mesophiles grow optimally around 37\text{^\text{o}C}, and thermophiles prefer high temperatures (50\text{^\text{o}C}\text{--}60\text{^\text{o}C}).

What atmospheric conditions are required by microaerophiles and capnophiles?

Microaerophiles require reduced oxygen levels ($5\text{\%}\text{--}6\text{\%}\text{ O}_2$), whereas capnophiles require enriched carbon dioxide levels ($5\text{\%}\text{--}10\text{\%}\text{ CO}_2$).

What occurs during each of the four phases of the bacterial growth curve?

1. Lag Phase: Preparation for division with no net population increase; 2. Exponential (Log) Phase: Rapid logarithmic cell division; 3. Stationary Phase: Balanced growth and death rates due to nutrient depletion; 4. Death Phase: Nonviable dying cells exceed viable cell formation.

What are the net energy yield outputs of the Embden-Meyerhof-Parnas (EMP) pathway and Entner-Doudoroff pathway?

The EMP pathway yields a net $2\text{ ATP}$ and $2\text{ NADH}$ per glucose molecule, whereas the Entner-Doudoroff pathway yields $1\text{ NADPH}$ per glucose molecule.

What defines transformation as a mechanism of horizontal gene transfer?

Transformation is the direct uptake and incorporation of naked or free environmental DNA by a competent bacterial host.

How do transduction and lysogeny operate in bacterial genetics?

Transduction is the transfer of bacterial DNA mediated by a bacteriophage; lysogeny occurs when a temperate phage integrates its DNA into the host genome without immediate cell lysis.

How is DNA transferred during bacterial conjugation?

DNA is transferred via direct cell-to-cell contact through a sex/conjugation pilus driven by an F-factor plasmid from a donor cell ($\text{F}^+$) to a recipient cell ($\text{F}^-$).

How do restriction enzymes protect bacteria from foreign viral DNA without harming their own genome?

They recognize and cut foreign DNA at specific nucleotide sequences while the host bacterial DNA is protected from cleavage via methylation.