Microbiology quiz 1

Hippocrates

The "father of Western medicine" who believed diseases had natural causes

Thucydides

Observed that survivors of the Athenian plague possessed immunity

Marcus Terentius Varro

Proposed that minute creatures not visible to the eye cause disease

Antonie van Leeuwenhoek

First to observe "animalcules" (bacteria and protists) in 1675

Robert Hooke

First to describe "cells" while viewing cork in 1665

Louis Pasteur

Discovered fermentation and developed pasteurization and vaccines

Robert Koch

Linked specific microbes to specific diseases like anthrax and cholera

Carolus Linnaeus

Developed the first standard taxonomic system using Genus and species

Binomial nomenclature

Scientific naming system where Genus is capitalized and species is lowercase

Carl Woese

Used small subunit rRNA to create the three-domain tree of life

Three Domains of Life

Archaea, Bacteria, and Eukarya

LUCA

Acronym for the Last Universal Common Ancestor of all life

Horizontal gene transfer

Transfer of DNA between existing cells, common in bacterial evolution

Refraction

The bending of light as it passes from one medium to another; most important concept in microscopy

Refractive index

The extent to which a material slows the transmission speed of light

Magnification

The ability of a lens to enlarge the image of an object

Resolution

The ability to distinguish two separate points in an image

Numerical aperture

The ability of a lens to gather light

Contrast

Visible differences between parts of a specimen and the background

Total Magnification

Ocular magnification multiplied by objective magnification

Field of View

The area visible through the lens; gets smaller and dimmer as magnification increases

Immersion oil

Used with 100x lenses to minimize light refraction because it has a refractive index similar to glass

200nm

The resolution limit for standard light microscopes

Brightfield microscope

Standard microscope producing dark images on a light background; usually kills specimens through staining

Darkfield microscope

Uses an opaque disk to show bright objects on a dark background; ideal for live, unstained spirochetes

Phase-contrast microscope

Uses interference to view live, unstained specimens and structures like endospores

DIC microscope

Uses two polarized light beams to produce high-contrast, 3D-appearing images

Fluorescence microscope

Uses fluorochromes and UV light to identify pathogens via immunofluorescence

Confocal microscope

Uses a laser to scan multiple Z-planes, creating high-resolution 3D images of thick specimens like biofilms

Two-photon microscope

Uses infrared light to view thick tissues like brain slices with minimal damage

TEM

Electron microscope that passes beams through thin sections to see internal structures

SEM

Electron microscope that bounces electrons off surfaces to create 3D surface images

STM/AFM

Scanning probe microscopes that can visualize individual atoms and molecular surfaces

Fixation

Attaching cells to a slide via heat or chemicals (like formalin) to preserve structure

Basic dye

A stain with a positive charge (e.g., methylene blue, crystal violet) that sticks to negative cell structures

Acidic dye

A stain with a negative charge (e.g., eosin, rose bengal) that is often repelled by cells, staining the background

Simple staining

Uses a single dye to emphasize basic specimen size and shape

Differential staining

Uses multiple stains to distinguish between organisms based on cell properties

Gram stain steps

1. Crystal Violet, 2. Iodine (mordant), 3. Ethanol (decolorizer), 4. Safranin

Gram-positive result

Bacteria appear purple because of a thick peptidoglycan cell wall

Gram-negative result

Bacteria appear pink because of a thin peptidoglycan layer and an outer membrane

Acid-fast stain

Used to detect waxy mycolic acids in cell walls like Mycobacterium tuberculosis

Endospore stain

Uses malachite green and heat (mordant) to identify dormant survival structures

Capsule stain

A negative staining technique (using India ink) that leaves a clear halo around virulent cells

Flagella stain

Uses a tannic acid mordant to thicken thin appendages for visualization

Endosymbiotic Theory

States mitochondria and chloroplasts originated as ancient free-living bacteria

Plasmids

Small, circular, extrachromosomal DNA loops often carrying antibiotic resistance

70S Ribosomes

Size of ribosomes found in prokaryotes and within eukaryotic mitochondria/chloroplasts

Peptidoglycan

Primary component of bacterial cell walls; targeted by penicillin

LPS

Toxin found in the outer membrane of Gram-negative bacteria; contains Lipid A and O antigen

Periplasmic space

Gel-filled space between the inner and outer membranes of Gram-negative bacteria

Quorum sensing

Bacterial communication via autoinducers to coordinate behavior like bioluminescence

Binary fission

The primary asexual reproduction method in prokaryotes

Selective permeability

The property of the plasma membrane that controls what enters and exits the cell

Facilitated diffusion

Passive movement of large or charged molecules across a membrane via protein channels/carriers

Active transport

Movement of molecules against a concentration gradient requiring ATP energy

Crenation

Shriveling of a cell lacking a cell wall in a hypertonic environment

Plasmolysis

The plasma membrane detaching from the cell wall in a hypertonic environment

Mitochondrial matrix

The internal site where many metabolic enzymes are located in eukaryotes

Cristae

Invaginations of the inner mitochondrial membrane that increase surface area for ATP production

Thylakoids

The third membrane system in chloroplasts where photosynthesis occurs

Mutualism

Symbiosis where both populations benefit, such as Bacteroides in the human gut

Amensalism

Symbiosis where Population A is harmed and Population B is unaffected

Commensalism

Symbiosis where one population benefits and the other is unaffected

Neutralism

Symbiosis where neither population is affected by the other

Parasitism

Symbiosis where one population benefits and the other is harmed

Resident microbiota

Microbes that constantly live in or on our bodies

Transient microbiota

Microbes only temporarily found in the human body

Bergey’s Manuals

The standard references for identifying and classifying prokaryotes

Nitrogen fixation

The conversion of atmospheric nitrogen (N2) into ammonia (NH3) for plants

Rhizobium

Nitrogen-fixing bacteria found in the root nodules of legumes

Alphaproteobacteria

Class of bacteria including oligotrophs and obligate intracellular pathogens

Rickettsia rickettsii

Causative agent of Rocky Mountain spotted fever; transmitted by ticks

Bordetella pertussis

Betaproteobacteria that causes whooping cough

Neisseria gonorrhoeae

Fastidious betaproteobacteria that causes gonorrhea

Pseudomonas aeruginosa

Gammaproteobacteria that forms biofilms in the lungs of cystic fibrosis patients

Haemophilus influenzae

Causes respiratory infections but, despite its name, does not cause the flu

Vibrio cholerae

Comma-shaped bacterium that causes severe dehydration via cholera

Helicobacter pylori

Epsilonproteobacteria that causes chronic gastritis, stomach ulcers, and cancer

Chlamydia trachomatis

Nonproteobacteria that causes an STI and trachoma (blindness)

Elementary body

The infectious, metabolically inactive form of Chlamydia

Reticulate body

The non-infectious, actively dividing form of Chlamydia

Spirochetes

Thin, spiral bacteria with an internal axial filament for motility

Treponema pallidum

Spirochete identified by darkfield microscopy that causes syphilis

Borrelia burgdorferi

Spirochete transmitted by ticks that causes Lyme disease and "bull's eye" rash

Mycobacterium tuberculosis

High G+C Gram-positive bacterium that causes TB; identified by acid-fast staining

Streptomyces

Genus of Actinobacteria that produces two-thirds of clinical antibiotics

Bacillus anthracis

Low G+C Gram-positive rod that causes anthrax

Clostridium tetani

Endospore-former that causes tetanus (spastic paralysis)

Mycoplasma pneumoniae

The smallest known bacteria; lacks a cell wall; causes walking pneumonia

Staphylococcus aureus

Gram-positive cocci known for causing skin infections and antibiotic resistance

Halophiles

Archaea that thrive in extremely salty environments

Trophozoite

The active feeding and growth stage of a protozoan life cycle

Cyst

The dormant, protective stage of a protozoan life cycle

Schizogony

Asexual reproduction in some protozoa where the nucleus divides many times before cell division

Entamoeba histolytica

Amoebozoa transmitted by fecal cysts that causes amoebic dysentery

Naegleria fowleri

The "brain-eating amoeba" found in warm fresh water

Apicomplexans

Intracellular parasites with a specialized apical complex for entering host cells

Plasmodium

Apicomplexan transmitted by the Anopheles mosquito that causes malaria

Sporozoite

The infective stage of Plasmodium injected into humans by a mosquito