Ch3 Prokaryotes viruses ( Archana and Bacteria)

Q: What literal etymological meaning describes cells that lack a membrane-defined nuclear envelope surrounding their genetic material?

A: "Free nucleus" or "before nucleus" (Prokaryote)

Q: Which cell type is significantly larger in physical volume and structurally more complex when compared to prokaryotes?

A: Eukaryotic cells

Q: Which cell type features distinct membrane lipid compositions, structurally different ribosomes, and specialized histone-like proteins associated with nucleic acids?

A: Eukaryotic cells

Q: Is the presence or absence of a membrane-bound nucleus the only defining feature between prokaryotic and eukaryotic cells?

A: No, it is only one definitional feature among numerous biochemical and structural differences.

Q: What two distinct domains comprise all prokaryotic organisms?

A: Bacteria and Archaea

Q: Which domain of prokaryotes serves as the primary focus of medical microbiology due to extensive research and high impact on human health, physiology, and infectious disease?

A: Bacteria

Q: Which domain represents unique cellular entities possessing distinct cell wall chemistry and lipid biochemistry separate from bacteria?

A: Archaea

Q: What is the predominant lifestyle of bacteria in natural environments despite being cellularly unicellular?

A: Living within complex, mixed-species communities

Q: Do bacteria communicate only within their own species, or across multiple species as well?

A: They maintain dynamic communication across and within species (intraspecies and interspecies communication).

Q: What cellular process involves bacteria monitoring neighboring population density and species composition?

A: Quorum sensing

Q: What process allows bacteria to tally local population density ("vote for their presence") and alter gene expression simultaneously across the population?

A: Quorum sensing

Q: What pathogenic strategy involves bacteria sitting quietly without expressing virulence factors until a critical cell density is reached before launching a coordinated infection to overwhelm host defenses?

A: Quorum sensing activation (density-dependent pathogenic behavioral modification)

Q: What are macroscopic aggregations of bacteria cultivated on solid laboratory media (such as agar plates)?

A: Colonies

Q: What microbial structures are visible to the naked eye as discrete dots, mounds, or circular growths on agar?

A: Colonies

Q: What are continuous sheets or films of microorganisms encased in a self-produced extracellular matrix adhering to living or non-living surfaces?

A: Biofilms

Q: What oral biofilm forms on tooth enamel (felt as a fuzzy layer upon waking) due to unbrushed plaque, largely driven by Streptococcus mutans?

A: Dental plaque (oral biofilm)

Q: On what natural tissue structures and implanted medical devices (e.g., eardrums, central lines, IV ports, urinary catheters, pacemakers, insulin pumps) do biofilms readily form?

A: Indwelling/implanted medical devices and natural host tissue structures

Q: What bacterial source continuously seeds off into surrounding host fluids, serving as a persistent origin of recurrent or systemic bloodstream infections?

A: Microbes encased within biofilms

Q: What term refers to the microscopic shape of an individual bacterial cell?

A: Morphology

Q: What is the standard condition wherein all cells of a given bacterial species exhibit a single, uniform shape under the microscope (e.g., Escherichia coli)?

A: Monomorphism

Q: What phenomenon occurs when cells of a single species vary significantly in shape and size within a single population, presenting diagnostic challenges?

A: Pleomorphism

Q: What is a spherical or round-shaped bacterial cell called?

A: Coccus (plural: Cocci)

Q: What is a cylinder- or rod-shaped bacterial cell called?

A: Bacillus (plural: Bacilli)

Q: What is a curved, comma-shaped rod called (e.g., Vibrio cholerae)?

A: Vibrio

Q: What is a rigid corkscrew-shaped spiral cell that uses external flagella to propel itself (analogous to an uncooked rotini noodle)?

A: Spirillum (plural: Spirilla)

Q: What is a flexible corkscrew-shaped spiral cell that utilizes an internal axial filament (periplasmic flagellum) to bore through viscous fluids (analogous to a cooked rotini noodle)?

A: Spirochete

Q: What term describes the spatial pattern and grouping of cells resulting from cellular division (binary fission)?

A: Cellular arrangement

Q: What process involves cell enlargement, chromosome replication, and division into two equal daughter cells?

A: Binary fission

Q: What arrangement occurs when offspring cells separate completely following division?

A: Single arrangement

Q: What coccal arrangement consists of pairs of two attached spherical cells (e.g., Neisseria gonorrhoeae) produced by division in one plane?

A: Diplococcus

Q: What coccal arrangement consists of linear chains of cocci resembling a string of pearls (e.g., Streptococcus pyogenes) produced by division in one plane?

A: Streptococcus

Q: Does the term Streptococcus serve as a formal taxonomic genus name, a lowercase structural descriptor, or both?

A: Both (taxonomic genus and structural descriptor)

Q: What coccal arrangement consists of a square packet containing four cocci produced by division in two perpendicular planes?

A: Tetrad

Q: What coccal arrangement consists of a cubical packet containing eight (or multiples of eight) cocci produced by division along three perpendicular axes ($x$, $y$, $z$)?

A: Sarcina

Q: What coccal arrangement consists of random, irregular clusters of cocci resembling bunches of grapes produced by division in multiple irregular planes?

A: Staphylococcus

Q: Why are bacillary arrangements restricted strictly to single, diplobacillus, streptobacillus, and palisade patterns?

A: Because bacilli divide strictly along their short transverse axis (a single plane) and lack perpendicular division planes.

Q: What bacillary arrangement features isolated individual rods?

A: Single

Q: What bacillary arrangement consists of pairs of two rod-shaped cells?

A: Diplobacillus

Q: What bacillary arrangement consists of linear chains of rod-shaped cells?

A: Streptobacillus

Q: What bacillary arrangement is formed when cells in a chain fold back against one another along flexible hinges, producing a side-by-side, accordion-like alignment?

A: Palisade

Q: Can bacilli form tetrads, sarcinae, or staphylobacillary arrangements?

A: No, due to the complete absence of perpendicular division planes.

Q: What cell arrangements do vibrios, spirilla, and spirochetes almost exclusively form after dividing along their short axis?

A: Individual single cells

Q: Into what two main functional categories are bacterial appendages divided?

A: Appendages for motility, and appendages for surface attachment or intercellular transfer

Q: What is the basic structure of a bacterial flagellum?

A: A thin, structurally simple, hollow protein tube extending from the cell wall.

Q: What is the primary function of bacterial flagella?

A: Directional movement toward favorable stimuli (nutrients, light, water) or away from hostile environments (extreme pH, toxic compounds, osmotic pressure).

Q: What mechanism of motion produces the characteristic "run and tumble" movement pattern of bacterial flagella?

A: $360^\circ$ rotation like a motorboat propeller

Q: How do eukaryotic flagella structurally and functionally differ from bacterial flagella?

A: Eukaryotic flagella are significantly thicker, membrane-enclosed, filled with cytoplasm/microtubules, and move in a smooth, undulating wave pattern instead of rotating $360^\circ$.

Q: What term describes a cell with a single flagellum at one pole?

A: Monotrichous

Q: What term describes a cell with a tuft or cluster of flagella emerging from a single site?

A: Lophotrichous

Q: What term describes a cell with flagella projecting from both opposing poles?

A: Amphitrichous

Q: What term describes a cell with flagella dispersed randomly over its entire outer surface?

A: Peritrichous

Q: What term describes a cell with a complete absence of flagella?

A: Atrichous

Q: What group of bacteria uniquely possesses axial filaments (periplasmic flagella)?

A: Spirochetes

Q: Where are axial filaments located within the spirochete cell structure?

A: Wrapped around the cell body within the periplasmic space beneath an outer sheath.

Q: What movement capability do axial filaments provide to spirochetes?

A: A corkscrew rotation that allows the bacterium to bore effectively through thick, viscous host secretions and mucosal tissues.

Q: What are short, bristle-like, hollow protein projections present in high numbers across the bacterial cell surface?

A: Fimbriae

Q: What is the primary function of fimbriae?

A: Adhesion to host tissues and environmental surfaces.

Q: How do fimbriae act as essential virulence factors for pathogens like Neisseria gonorrhoeae and Escherichia coli?

A: They enable pathogens to colonize host membranes (e.g., binding to mucosal epithelial cells or anchoring in the gastrointestinal tract).

Q: What are long, hollow tubular structures constructed from the protein pilin, typically present singly or in small numbers per cell?

A: Pili (Conjugation pili)

Q: What process is mediated by pili between compatible bacterial cells?

A: Bacterial conjugation (the direct transfer of plasmid DNA)

Q: What are extremely thin, short membrane extensions linking adjacent bacterial cells?

A: Nanotubes (Nanowires)

Q: What is the function of bacterial nanotubes (nanowires)?

A: Facilitating direct intercellular transfer of nutrients, ATP, signaling molecules, and cytoplasmic components.

Q: What protective outer layer consists of identical protein subunits arranged in a repetitive, chain-mail-like pattern?

A: S-Layer (Surface Layer)

Q: Under what conditions do bacteria produce an S-layer, and what happens when they are continuously cultured in rich lab media?

A: They produce it under hostile environmental stress; continuous rich lab culturing often causes them to lose this ability.

Q: What surface coating is composed of polysaccharides (carbohydrates) that may be complexed with proteins?

A: Glycocalyx

Q: How does the glycocalyx facilitate surface attachment and biofilm formation (e.g., in Streptococcus mutans)?

A: It forms an adhesive matrix on surfaces (like tooth enamel) by metabolizing sugars, creating a scaffold for secondary microbes to attach.

Q: How does the glycocalyx protect bacterial cells against desiccation and host immunity?

A: It retains moisture to prevent lethal water loss and provides a slippery coat that prevents host phagocytes from binding and engulfing the pathogen.

Q: What type of glycocalyx is unorganized, loose, and easily washed off or detached from the cell body?

A: Slime layer

Q: What type of glycocalyx is dense, highly structured, rigid, and tightly bound to the cell wall?

A: Capsule

Q: What appearance does an encapsulated cell have in a negative capsule stain under the microscope?

A: A clear halo surrounding the cell against a dark background.

Q: What distinct colony morphology do encapsulated bacterial strains display on agar plates?

A: Mucoid, shiny, snotty, or slimy colonies.

Q: Is a cell wall present in nearly all bacterial species?

A: Yes.

Q: What are the primary functions of the bacterial cell wall?

A: Imparting cellular shape, providing structural rigidity, and preventing osmotic lysis (cell rupture) under hypotonic conditions.

Q: What macromolecule is found exclusively within bacterial cell walls?

A: Peptidoglycan (murein)

Q: Which two alternating amino sugars make up the long glycan chains of peptidoglycan?

A: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Q: How are parallel sugar chains linked together in peptidoglycan to form a mesh-like network?

A: Cross-linked by short peptide chains of amino acids.

Q: What is the Gram stain procedure?

A: A four-step differential staining technique that categorizes bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall architecture.

Q: What defines the cell wall architecture of Gram-positive bacteria?

A: A thick, multi-layered sheet of peptidoglycan situated directly outside the plasma membrane.

Q: What color do Gram-positive cells stain in a Gram stain?

A: Purple

Q: What teichoic acid is confined strictly to the peptidoglycan layer of Gram-positive cell walls?

A: Wall Teichoic Acid

Q: What teichoic acid spans the peptidoglycan sheet and anchors directly into the underlying plasma membrane?

A: Lipoteichoic Acid

Q: What are the key functions of teichoic acids in Gram-positive cell walls?

A: Imparting a negative surface charge to attract positive ions, assisting in cell wall maintenance and binary fission, and serving as serological identification markers.

Q: Why do Gram-positive cells appear deep purple under light microscopy?

A: Because their thick cell wall retains the primary crystal violet-iodine complex.

Q: What defines the cell wall architecture of Gram-negative bacteria?

A: A thin, single layer of peptidoglycan suspended in a periplasmic space between the inner plasma membrane and an asymmetric outer membrane.

Q: What color do Gram-negative cells stain in a Gram stain?

A: Pink

Q: What is the outer membrane of Gram-negative bacteria composed of?

A: A phospholipid bilayer shielding the peptidoglycan layer.

Q: What channel proteins span the Gram-negative outer membrane to regulate molecule transport into the periplasmic space?

A: Porin proteins

Q: What complex molecule is located on the outer leaflet of the Gram-negative outer membrane?

A: Lipopolysaccharide (LPS)

Q: What lipid component of Lipopolysaccharide (LPS) is also known as Endotoxin?

A: Lipid A

Q: Under what conditions is Lipid A (Endotoxin) released from Gram-negative bacteria?

A: Upon cell lysis or cell death.

Q: What severe systemic pathological responses are induced by Endotoxin (Lipid A) release?

A: High fever, violent diarrhea, severe inflammation, vascular collapse, septic shock, and disseminated intravascular coagulation (DIC).

Q: Do all Gram-negative species release the exact same amount of endotoxin?

A: No, endotoxin expression varies among species, with high producers capable of causing rapid endotoxic shock.

Q: Why do Gram-negative cells appear pink under light microscopy?

A: They lose crystal violet during decolorization and pick up the safranin counterstain.

Q: How fast are Gram stain diagnostic results available compared to culture results?

A: Within approximately $30\,\text{minutes}$, compared to days or weeks for culture results.

Q: How do Gram stain results guide immediate pharmacological selection?

A: They dictate empirical antibiotic choices based on differential drug susceptibilities (e.g., more drugs target Gram-positive walls).

Q: How do Gram stain results assist clinical prognosis?

A: They help predict expected toxin production (endotoxins vs. exotoxins), clinical signs, and disease progression.

Q: What structural cell wall component is entirely absent in Domain Archaea?

A: Peptidoglycan (they use pseudomurein or protein coats instead).

Q: What are L-Forms (L-Phase Variants)?

A: Strains of bacteria that naturally possess a cell wall but lose it during their lifecycle (often in response to antibiotics like penicillin or lab adaptation).

Q: What is the clinical significance of L-Form bacteria?

A: They are implicated in persistent, chronic, or recurrent infections that resist standard cell-wall-targeting therapies.

Q: What bacterial genus naturally lacks a cell wall entirely and is genetically incapable of synthesizing peptidoglycan?

A: Mycoplasma