Intro to Microbiology 8/8/25

These vocabulary flashcards cover essential terms and definitions from the lecture on microbiology, emphasizing microbial classification, cell structure, staining, key pathogens, and clinically relevant concepts needed for exam preparation.

Microorganism

A microscopic living organism (virus, bacterium, protozoan, mold/yeast) that replicates within a host and cannot be seen with the naked eye. Massive reproduction.

Macroorganism

Infectious stage matures into reproductive stage. Visble with naked eye

Normal flora (Microbiome)

The community of microbes that normally inhabit the skin and mucous membranes, offering protection, vitamin production, and competitive exclusion of pathogens.

Prokaryote

Cell type lacking a true nucleus and organelles; always unicellular, divides by binary fission, has circular DNA and simultaneous transcription-translation (e.g., bacteria). 1 chromosome, some have plasmids. Still has plasma membrane, cytoplasm, ribosomes, and DNA genome.

Eukaryote

Cell type with a membrane-bound nucleus, organelles, linear chromosomes, and separate transcription and translation; includes protozoa, fungi, helminths.

Binary fission

Asexual reproductive process in which a prokaryotic cell duplicates its DNA and splits into two identical daughter cells.

Plasmid

Extrachromosomal circular DNA in bacteria that can carry antibiotic-resistance or toxin genes and replicate independently of the chromosome.

Microbial nomenclature

family, genus, species, sometimes sub species.

E. coli 0157:h7

Causes bloody diarrhea and is associated with hemolytic uremic syndrome. Caused by a specific toxin that only this specific E. coli expresses

Bacterial classification

Shape/arrangement (morphology), cell features, nutritional requirements, oxygen requirements, biochemical reactions, serology/antigen test, reservoirs/hosts/habitat, insect vector

Gram-positive bacteria

Bacteria with a thick peptidoglycan cell wall, retain crystal violet stain, appear purple, and often contain teichoic and lipoteichoic acids.

Cell wall

Gram positive trait. External to plasma membrane made of 3d proteins and sugars. very strong, supports and shapes cell. Made of peptidoglycan which is targeted by many abx. Degradable by lysozymes.

Bacteria cell membrane

Phospholipid bilayer with no sterols, no cholesterol, and diff lipid. Functionally equivalent to euk cell membrane

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS); lose crystal violet, take up safranin, appear pink/red. Lipid A portion is toxic/endotoxin.

Normal flora/microbiome

Cover the surface of skin, mucous membranes. Adherence first step in establishing infection. Can produce substances that can kill pathogens. Colon flora ferment indigestible carbohydrates for us, produce vitamins (e.g., K and B12). Skin flora produce fatty acids that lowers pH, which prevents some pathogens from growing. Lactobacillus in vagina produces acid to keep the pH low, which prevents overgrowth of Gardnerella

Escherichia coli and other coliforms location

colon, vagina, outer urethra

Gardnerella vaginalis location

vagina

Lactobacillus species location

mouth, colon, vagina

Staphylococcus

gram positive cocci in grape like clusters

escerichia

gram negative rods

bacillus

large gram positive rods

Staphylococcus aureus location

nose, skin

mycoplasma

doesnt gram stain. no peptidoglycan. 3 membranes and sterols. unique!

chlamydiae, rickettsiae

can’t gram stain. obligate intercellular bacteria. weird peptidoglycan. uses other stains, ex) Giemsa

chlamydia

chlamydia can’t make ATP, they steal it. Has 2 lifecycle forms, reticulate bodies (replicate in host cell cytoplasm) and elementary bodies (in environment outside host cells, not replicating but infectious)

rickettsiae

obligate intracellular. limited metabolic abilities (no DNA bases or ATP). weak cell wall. Stain with Giemsa

mycobacterium

unique acidic cell walls full of lipids. repel most dyes but we have a special stain - acid fast staining/ziehl neelsen.

tuberculosis and leprosy.

unique mycolic acids and lipids in cell envelope. hidden peptidoglycan.

Ziehl neelsen acid fast stain

A staining technique used to identify mycobacteria, particularly those with waxy cell walls. It allows for the visualization of acid-fast bacteria, such as Mycobacterium tuberculosis. Debris is blue, bacterial rods are pink. It involves multiple steps including application of carbol fuchsin, heat, decolorization with acid-alcohol, and counterstaining with methylene blue.

spore stain

for bacteria that make endospores

silver stain

for bartonella henslae, cat scratch fever

fluorescent stains

legionella

Options besides gram stain

PCR, intracellular inclusions, rapid tests for antigens, fluorescence, serology IgM/IgG

Viridans streptococci location

mouth, nasopharynx

Peptidoglycan

Rigid, mesh-like polymer of sugars (NAG & NAM) and peptides forming the bacterial cell wall; target of β-lactam antibiotics and lysozyme.

Gram staining

1st: crystal violet to bind to peptidoglycan cell wall if present. 2nd: iodine to form complexes. 3rd: decolorization with alcohol or acetone. 4th: counterstain with safranin that binds to gram negative.

Lipopolysaccharide (LPS)

Major component of Gram-negative outer membrane composed of Lipid A, core polysaccharide, and O-antigen; also called endotoxin.

Lipid A

Toxic portion of LPS that triggers Toll-like receptor 4, cytokine storm, fever, hypotension, DIC, and Gram-negative sepsis.

O-antigen

Polysaccharide side chain of LPS that varies between strains and can be antiphagocytic; used in serotyping (e.g., E. coli O157).

Teichoic acid

Polyalcohol polymers anchored in the peptidoglycan of Gram-positive bacteria; important for cell wall stability and antigenicity.

Lipoteichoic acid

Teichoic acid linked to the plasma membrane of Gram-positive bacteria; elicits host immune responses.

Periplasmic space

Region between the inner and outer membranes of Gram-negative bacteria containing enzymes and transport proteins.

Outer membrane

Gram-negative lipid bilayer external to peptidoglycan that contains LPS, porins, and provides antibiotic resistance.

Bacterial plasma membrane

Phospholipid bilayer lacking sterols (except Mycoplasma); site of electron transport, ATP synthesis, nutrient transport, and secretion.

Endotoxin

Collective term for LPS released from dying Gram-negative bacteria; causes potent innate immune activation and septic shock.

Coccus (cocci)

Spherical bacterial shape; e.g., Staphylococcus aureus and Streptococcus pyogenes.

Bacillus (bacilli)

Rod-shaped bacterium; e.g., Escherichia coli, Bacillus anthracis.

Coccobacillus

Short, plump rod with features of both cocci and bacilli; e.g., Haemophilus influenzae.

Vibrio / Curved rod

Comma-shaped bacterium with one or more curves; e.g., Vibrio cholerae.

Spirochete

Flexible, spiral-shaped bacterium propelled by axial filaments; e.g., Treponema pallidum.

Filamentous bacteria

Rod-shaped bacteria that remain attached, forming long threads resembling fungi; e.g., Nocardia species.

Diplococci

Pair arrangement of cocci (two cells together); e.g., Neisseria gonorrhoeae.

Chains (streptococci)

Linear arrangement of cocci produced by division in one plane; characteristic of Streptococcus species.

Clusters (staphylococci)

Grape-like grouping of cocci produced by division in multiple planes; characteristic of Staphylococcus species.

Obligate intracellular bacterium

Bacterium that can replicate only inside host cells because of metabolic dependence; e.g., Chlamydia, Rickettsia.

Mycoplasma

Bacteria lacking peptidoglycan, possessing sterol-containing triple membranes, and therefore not visible on Gram stain; cause atypical pneumonia.

Mycobacterium

Genus of acid-fast bacilli with lipid-rich, waxy cell walls containing mycolic acids; includes M. tuberculosis and M. leprae.

Acid-fast stain

Ziehl-Neelsen technique using carbol-fuchsin and acid-alcohol to detect mycolic-acid–rich bacteria (e.g., Mycobacterium).

Giemsa stain

Differential stain used to visualize intracellular pathogens (Chlamydia, Rickettsia) and blood parasites by staining nucleic acids.

Gram stain

Four-step differential stain (crystal violet, iodine, alcohol, safranin) that categorizes bacteria as Gram-positive or Gram-negative.

Crystal violet

Primary purple dye in Gram stain that binds thick peptidoglycan of Gram-positive bacteria.

Safranin

Counterstain in Gram procedure that colors Gram-negative bacteria pink/red after decolorization.

Lysozyme

Host enzyme in tears and saliva that cleaves peptidoglycan, weakening bacterial cell walls.

Binary arrangement terms

Descriptors like single, pairs, chains, clusters that aid bacterial identification beyond shape alone.

Enterobacteriaceae

Large family of Gram-negative rods inhabiting intestines; includes Escherichia, Salmonella, Klebsiella, etc.

Escherichia coli O157:H7

Specific serotype of E. coli producing Shiga-like toxin, causing bloody diarrhea and hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS)

Triad of hemolytic anemia, thrombocytopenia, and acute renal failure often triggered by E. coli O157:H7 toxin.

Lactobacillus

Normal vaginal flora that ferments glycogen to lactic acid, maintaining acidic pH and preventing Gardnerella overgrowth.

Gardnerella vaginalis

Gram-variable bacterium that overgrows when vaginal pH rises, leading to bacterial vaginosis.

Opportunistic infection

Disease caused by normal flora when they access normally sterile sites or when host defenses are compromised.

Lipoteichoic-acid–induced inflammation

Host immune response to Gram-positive cell wall components (lipoteichoic acid) causing fever and inflammation.

TLR4 (Toll-like receptor 4)

Innate immune receptor that specifically recognizes LPS/Lipid A, initiating cytokine release and septic shock.

Cytokine storm

Massive, uncontrolled release of pro-inflammatory cytokines leading to fever, capillary leak, DIC, and shock.

Disseminated intravascular coagulation (DIC)

Pathological activation of clotting throughout the body causing petechiae, bleeding, and organ failure, often triggered by endotoxin.

Meningococcemia (meningococcal septicemia)

Severe bloodstream infection with Neisseria meningitidis characterized by fever, petechiae, and fulminant septic shock. Gram neg. cocci. Meningitis.

Teichoic-acid–rich cell wall

Structural feature distinguishing Gram-positive bacteria such as Staphylococcus aureus from other microbes.

Endospore stain

Special stain (e.g., malachite green) used to visualize heat-resistant spores produced by Bacillus and Clostridium species.

Silver stain

Histological stain that deposits silver on certain pathogens (e.g., Bartonella, Legionella), improving visibility.

Fluorescent antibody stain

Technique using fluorescent-labeled antibodies to detect specific microbial antigens directly in clinical specimens.

Obligate aerobe

Bacterium that requires oxygen for growth due to reliance on oxidative phosphorylation; e.g., Pseudomonas aeruginosa.

Facultative anaerobe

Bacterium that can grow with or without oxygen, using aerobic respiration or fermentation; e.g., E. coli.

Oxidase test

Biochemical assay detecting cytochrome c oxidase; positive in Pseudomonas, Neisseria, negative in Enterobacteriaceae.

Lactose fermentation

Metabolic trait where bacteria (e.g., E. coli) ferment lactose to acid, identified on MacConkey agar.

Serotyping

Classification of microbes based on surface antigens (e.g., O, H, K antigens in Enterobacteriaceae).

Catalase test

Enzymatic assay distinguishing catalase-positive Staphylococcus (bubbles) from catalase-negative Streptococcus (no bubbles).

Coagulase test

Lab test differentiating pathogenic Staphylococcus aureus (coagulase-positive) from coagulase-negative staphylococci.

Antibiotic target – cell wall synthesis

Mechanism exploited by β-lactams and glycopeptides to inhibit peptidoglycan assembly, causing bacterial lysis.

Acidic vaginal pH

Protective low pH (~3.8-4.5) maintained by Lactobacillus-produced lactic acid that suppresses pathogens.

Endotoxin shock (LPS shock)

Life-threatening condition of fever, hypotension, DIC, and multiorgan failure due to massive LPS release.

Intracytoplasmic inclusion

Microscopic aggregation of replicating Chlamydia reticulate bodies within host cell cytoplasm, visualized by Giemsa or fluorescence.

Reticulate body

Metabolically active, non-infectious intracellular form of Chlamydia responsible for replication inside host cells.

Elementary body

Infectious, extracellular, metabolically inert form of Chlamydia that initiates new infections.