Microbiology: Microorganisms as Cells, Structure, and Metabolism Flashcards

Vocabulary practice flashcards generated from BIO425 Microbiology modules covering cell morphology, prokaryotic and eukaryotic structures, acellular agents, and microbial metabolism.

Total Magnification

The product of the magnifying powers of the objective lens and the ocular lens ($\text{Total Magnification} = \text{objective lens} \times \text{ocular lens}$).

Resolution

The ability to distinguish two separate points or objects as distinct, defining the clarity of an image.

Common Prokaryotic Cell Shapes

Round prokaryotic cells are termed cocci ($\text{sing. coccus}$), rod-shaped cells are termed bacilli ($\text{sing. bacillus}$), and curved rod-shaped cells are termed vibrios ($\text{sing. vibrio}$).

Common Prokaryotic Cell Arrangements

Groupings formed by prokaryotic cells during division, including pairs ($\text{diplococci}$), square groupings of four ($\text{tetrads}$), chains ($\text{streptococci}$), and clusters ($\text{staphylococci}$).

Mycoplasma pneumoniae

The smallest bacterium (0.1 proposal procedure \times 10^0 = 0.1\text{ }\frac{1}{10^6}\text{m} = 0.1 \times 10^{-6}\text{m} = 0.1\text{ }\text{\textmu m} wide) that lacks a cell wall and acts as an obligate parasite of tracheal and bronchial epithelial cells.

Epulopiscium fishelsoni

A giant bacterium that reaches sizes greater than 500\text{ }\text{\textmu m} in length.

Thiomargarita namibiensis

A large sulfur bacterium measuring greater than 200\text{ }\text{\textmu m} found in Namibian marine sediments.

Bacterial Cell Structural Organization

Division of bacterial structures into cell envelope (cell membrane, cell wall, glycocalyx/S layer), external appendages (flagella, pili, fimbriae), and cytoplasmic structures (ribosomes, nucleoid, plasmids, inclusions, cytoskeleton).

Peptidoglycan

A mesh-like cell wall polymer unique to bacteria composed of alternating helical strands of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by peptide chains.

Gram-Positive vs. Gram-Negative Cell Walls

Gram-positive walls consist of a thick peptidoglycan layer with teichoic acids; Gram-negative walls feature a thin peptidoglycan layer surrounded by an outer membrane containing lipopolysaccharides (LPS).

Lipopolysaccharide (LPS)

A toxin located in the outer membrane of Gram-negative bacteria composed of Lipid A, a core polysaccharide, and an O side chain (O antigen).

Glycocalyx

An outer polysaccharide coating existing as a loose shield (slime layer) or tightly bound layer (capsule) that protects against phagocytosis and desiccation while promoting surface adherence.

S Layer

A rigid, self-assembling surface layer of protein or glycoprotein that protects bacterial cells against ion and pH fluctuations, osmotic stress, enzymes, and host defenses.

Patterns of Flagellation

Bacterial flagellar arrangements including monotrichous (single flagellum), amphitrichous (flagellum at both ends), lophotrichous (cluster of flagella at one/both ends), and peritrichous (surrounding the cell).

Flagellar Base Structure

The anchoring component of the bacterial flagellum containing a stator that provides torque and a basal body (C and MS rings) that produces rotary movement.

Chemotaxis

Directional movement of an organism toward a chemical attractant or away from a repellent achieved by altering tumbling frequency and increasing run durations.

Sex Pili

Long, thick appendages ($1\text{ to }10/\text{cell}$) encoded by plasmid genes that are required for bacterial conjugation and DNA uptake.

Prokaryotic vs. Eukaryotic Ribosomes

Bacterial and archaeal ribosomes are $70\text{S}$ ($30\text{S}$ SSU with $16\text{S}$ rRNA; $50\text{S}$ LSU with $23\text{S}$ and $5\text{S}$ rRNAs), whereas eukaryotic ribosomes are $80\text{S}$ ($40\text{S}$ SSU with $18\text{S}$ rRNA; $60\text{S}$ LSU with $28\text{S}$, $5.8\text{S}$, and $5\text{S}$ rRNAs).

Bacterial Cytoskeletal Elements

Homologs of eukaryotic cytoskeletal structures in bacteria: FtsZ (tubulin homolog), MreB (actin homolog), and CreS (intermediate filament homolog).

Sporulation

A multi-step, non-reproductive developmental process in certain Gram-positive bacteria (e.g., Bacillus, Clostridium) that forms a dormant, highly resistant endospore under stress.

Hami and Cannulae

External structures of Archaea: hami are small grappling hooks used for attachment in biofilms; cannulae are hollow, tube-like structures connecting newly divided cells in thermophiles.

Bacterial vs. Archaeal Membrane Structure

Bacterial membranes consist of ester-linked fatty acid bilayers, whereas archaeal membranes contain ether-linked isoprene chains that can form lipid monolayers.

Pseudomurein

A cell wall polysaccharide found in some Archaea containing N-acetyltalosaminuronic acid instead of N-acetylmuramic acid.

Phytophthora infestans

A plant-pathogenic oomycete that forms filaments and sporangia on leaves, causing potato late blight, which led to the Irish potato famine.

Fungal Hyphae

Filamentous fungal cells that can be septate (divided by crosswalls) or coenocytic (non-septate, continuous multinucleated structures).

Basidium

A spore-bearing organ located in mushroom gills of Basidiomycetes that serves as the site for karyogamy and meiosis to produce sexual basidiospores.

Acellular Infectious Agents

Infectious non-cellular entities comprising viruses (protein and nucleic acid), viroids (RNA), satellites (RNA or DNA requiring a helper virus), and prions (protein only).

Nucleocapsid

The essential structure of a virus composed of viral nucleic acid (DNA or RNA) contained within a protein coat called a capsid.

Viroid

An infectious plant agent consisting of a closed, single-stranded circular RNA molecule with intra-strand base-pairing that does not encode any proteins.

Prion

An abnormal proteinaceous infectious particle lacking genetic material (DNA or RNA) that induces conformational changes in normal host proteins, leading to fatal neurodegenerative diseases.

Classifications of Organisms by Energy and Carbon Source

Nutritional categories based on energy source (phototroph vs. chemotroph), carbon/electron source (autotroph vs. heterotroph; lithotroph vs. organotroph), and specific substrate utilization.

Catabolism vs. Anabolism

Catabolism is the exergonic breakdown of complex molecules via oxidation that yields energy and reducing power; Anabolism is the endergonic biosynthesis of complex molecules via reduction that consumes energy and reducing power.

Central Dogma of Molecular Biology

The pathway of genetic information flow: replication ($\text{DNA} \rightarrow \text{DNA}$ via DNA Polymerase), transcription ($\text{DNA} \rightarrow \text{RNA}$ via RNA Polymerase), and translation ($\text{RNA} \rightarrow \text{Protein}$ via Ribosome).

Electron Transport Chain (ETC)

A membrane-bound series of electron carriers operating together to transfer electrons from donors like $\text{NADH}$ to a terminal electron acceptor while creating a proton gradient for ATP synthesis.

Substrate-Level Phosphorylation

The synthesis of ATP coupled directly to the exergonic breakdown or transfer of a phosphate group from a high-energy metabolic donor molecule to ADP.

Embden-Meyerhof Pathway

The most common glycolytic pathway for glucose degradation, yielding a net total of $2\text{ ATP}$, $2\text{ NADH}$, and $2\text{ pyruvate}$ molecules.

Calvin-Benson Cycle Equation

The overall summary reaction for hexose sugar formation from carbon dioxide: $6\text{CO}_2 + 18\text{ATP} + 12\text{NADPH} + 12\text{H}^+ + 12\text{H}_2\text{O} \rightarrow \text{glucose} + 18\text{ADP} + 18\text{P}_i + 12\text{NADP}^+$.

Bactoprenol Phosphate

A lipid carrier that binds peptidoglycan repeat units (NAG-NAM-pentapeptide) and transports them across the plasma membrane from the cytoplasm to the periplasmic space.

Biological Nitrogen Fixation

The enzymatic reduction of dinitrogen gas ($\text{N}_2$) to ammonia ($\text{NH}_3$) carried out by prokaryotes via the nitrogenase complex ($\text{N}_2 + 8\text{H}^+ + 8e^- + 16\text{ATP} \rightarrow 2\text{NH}_3 + \text{H}_2 + 16\text{ADP} + 16\text{P}_i$).