Microbiology Exam 1

microbiology

study of living things too small to be seen without magnification

microbes/microorganisms

organisms that are too small to be seen without magnification

ex: bacteria, viruses, fungi, helminths, protozoa

pathogen

microbe that causes a disease

infectious disease

disease caused by a pathogen

prokaryotes

“prenucleus”

organisms that don’t have nuclei or other organelles; predominantly unicellular (bacteria)

eukaryotes

“true nucleus”

organisms that have nuclei and other organelles w/ special functions; mostly multicellular (fungi, helminths, protozoa)

bacteriology

study of bacteria

virology

study of viruses

parasitology

study of protozoa + helminths

mycology

study of fungi

binomial nomenclature

standardization for naming microbes that has 2 parts: genus and the species

genus is capitalized; species is lowercase

ex: Staphylococcus aureus

Louis Pasteur (1800s)

developed pasteurization (heat-treatment process that kills harmful microbes + prevents spoilage in liquids w/out ruining the taste)

contributed to germ theory of disease (specific microbes cause fermentation, spoilage, and infectious diseases

Robert Koch (1800s)

established “Koch’s postulates” (series of steps that could establish whether an organism was pathogenic + what disease it caused)

Alexander Fleming (1900s)

discovered the antibiotic activity of penicillin (a stray mold spore contaminated a petri disc of Staphylococcus bacteria and killed the surrounding growth)

culture

introducing microorganisms to a medium that supports their growth + multiplication

classification

process of arranging microbes to groups based on similar characteristics

the five I’s

1) inoculation

2) incubation

3) isolation

4) inspection

5) identification

inoculation

adding a pathogen, antigen, or microbial sample to a medium to stimulate immunity or encourage growth

incubation

maintaining controlled environments (heat, humidity, oxygen) to promote the growth of a culture

isolation

separating a single species/strain of microorganism from a mixed population to create a pure culture

inspection

performing tests and observing

identification

using the information from inspection to determine the exact species or type of microorganism in a sample

medium

provides nutrients to microorganisms, allowing them to grow outside their natural habitat

types of cultures

pure: contains 1 species

mixed: contains 2 or more known species

contaminated: contains contaminants (unwanted/unknown species)

colony

discrete mound of cells

isolated colony

colony that was formed from a single cell; contains only 1 species

bacteria

independent, single-celled, prokaryotic organisms w/out a nucleus

1) nuclear material (DNA) is free inside the cell

2) walls are sturdy and made of peptidoglycan

3) have no complex, membrane-bounded organelles

5 main bacterial shapes

1) coccus - spherical shape

2) bacillus - rod/cylindrical shape

3) curved - shaped/curved rods

4) spirillum - spiral and rigid

5) spirochete - spiral and flexibile

coccobacillus shape

short, oval rod that looks halfway between a coccus (round sphere) and an elongated rod (bacillus)

what bacterial shape is this?

coccus (plural cocci)

what bacterial shape is this?

bacillus (plural bacilli)

what bacterial shape is this?

curved

what bacterial shape is this?

spirillum

what bacterial shape is this?

spirochete

external structures of bacteria

appendages:

1) flagella: motility

2) fimbria: attachment

3) pilus: connection

surface coatings:

1) capsule

2) slime layer

flagellum

long, whip-like structures used for cell motility via self-propulsion; allows bacteria to swim freely through aqueous habitats

fimbria

small, bristle-like fiber sprouting off the surface of a cell

used for attachment (stick to each other + surfaces) + establishing infection or colonization

pilus

long, rigid tubular structure used for connection + sharing genetic material

conjugation pili

partial transfer of DNA from 1 cell to another

slime layer

loose shield that protects bacteria from loss of water + nutrients

capsule

a layer tightly bound to the cell; denser + thicker than a slime layer

encapsulated bacteria

bacteria that has a capsule; more likely to cause pathogenesis b/c the capsules protect the bacteria against phagocytosis

phagocytosis

when phagocytes (immune cells) engulf bacteria to destroy them

biofilm

feature of the slime layer

mixed community of bacteria + other microbes attached to a surface + each other

can complicate treatments by acting as a shield that blocks medications + hides microorganisms from the immune system

cytoplasmic membrane

innermost layer

lipid bilayer (containing phospholipids) w/ proteins embedded within the membrane

cell wall

strong, structural support that keeps bacteria from collapsing

protects from lysis (disintegration/rupture of a cell)

made of peptidoglycan

gram positive vs. gram negative stain

gram positive - purple

gram negative - pink

differences in staining has to do w/ the peptidoglycan in the cell walls

gram-positive cell envelope

2 layers:

1) cytoplasmic membrane

2) cell wall: thick, homogenous sheath of peptidoglycan + lipoteichoic acid (LTA)

• LTA functions as the endotoxin of gram positive bacteria (not technically an endotoxin like LPS but works similarly)

gram-negative cell envelope

3 layers:

1) cytoplasmic membrane

2) cell wall: single, thin sheet of peptidoglycan and NO LTA

3) outer membrane: lipopolysaccharide (LPS)

• LPS is an endotoxin; stimulates immune reactions like fever/shock

benefit of an outer membrane for gram-negative bacteria

outer membrane acts as an extra barrier for gram-negative bacteria, making them impermeable to some antibiotics + therefore more difficult to inhibit/kill than gram-positive bacteria

exceptions of cell walls

1) some bacteria aren’t characterized as gram-positive or negative; must use an acid-fast stain (mycobacterium)

2) some bacteria don’t have a cell wall at all (mycoplasma)

3) some bacteria are so small we can’t determine the gram stain (rickettsia + chlamydia)

bacterial chromosome

single circular strand of DNA that contains most of the bacterial DNA

every bacterial cell has a bacterial chromosome

plasmids

non-essential pieces of DNA; double stranded circles

not every bacterial cell has plasmids

prokaryotic vs. eukaryotic ribosomes

eukaryotes have larger ribosomes than prokaryotes

endospores

dormant bodies produced by bacteria

hardiest of all life forms; can withstand extreme heat, drying, freezing, radiation, and chemicals

sporulation

process by which bacteria form endospores to survive harsh environmental conditions

not reproduction; only 1 endospore is made

germination

reverse process of sporulation where the spore wakes up and turns back into an active, growing cell when conditions are favorable

fungi

type of eukaryotic microbe w/ a defined nucleus + specialized organelles

can either be unicellular or multicellular

extracellular matrix of fungi

helps protect, adhere, and receive signals from other cells and the environment

cell wall of fungi

all fungi have cell walls to give them structural support/shape

built mostly from chitin + glycans; doesn’t have peptidoglycans like bacterial cell walls

cell membrane of fungi

phospholipid bilayer intermixed w/ sterols (give the membrane more structure)

internal structures of fungi

1) nucleus - contains DNA

2) lysosome - contains variety of enzymes

3) vacuole - storage

4) mitochondria - generates ATP for the cell

2 forms of fungi

1) yeasts - round/oval shape, asexual production

2) hyphae (molds) - long, threadlike cells

dimorphic fungi

can transition b/w yeast and mold forms depending on the growth conditions

yeasts at body temperature; molds at room temperature

morphology of yeasts vs. molds

yeasts: unicellular w/ smooth, creamy colonies

molds: multicellular w/ soft, hairy, or velvety colonies

mycelium

intertwining mass of hyphae that makes up a colony

different morphology of molds

1) septate hyphae - segmented

2) nonseptate hyphae - continuous cell

3) vegetative hyphae - growth phase, absorb nutrients from substrate

4) reproductive hyphae - branches from vegetative hyphae + forms spores (fungal reproductive bodies)

how do yeasts replicate?

“budding”: reproduce asexually by making identical copies of itself through mitosis

how do molds replicate?

asexual spore formation: result of mitotic division from 1 parent cell

sexual spore formation: spores formed through meiosis; increases genetic variation

fungal spores

microscopic reproductive units that help the fungus disperse throughout the environment

saprobes vs. parasites

saprobe fungi obtain nutrients from dead plants/animals

parasite fungi live in or on the body of a living host to acquire nutrients

parasite

requires a living host to complete its lifecycle

no benefits to the host; detrimental

ex: protozoa + helminths

protozoa

single-celled, microscopic eukaryotic organisms

most diverse class of microbes

all are unicellular

require living hosts to complete their life cycle

external structures of protozoa

1) flagella - used for mobility (overall movement)

2) cilia - used for motility (internal movement

3) pseudopodia - used for motility + phagocytosis

boundary structures of protozoa

1) cytoplasmic membrane

no cell wall; cell shape can be constant or always changing

internal structures of protozoa

1) ectoplasm - clear outer layer of cytoplasm used for pseudopod formation

Are protozoa similar to each other, or different?

protozoa are similar in their basic cellular design as unicellular eukaryotes but they are different in their shapes, movements, and ways of life

how do protozoa move?

by using the flagella (whip-like tails), cilia (hair-like structures), or pseudopodia (temporary extensions of the cell’s cytoplasm)

trophozoites

active, feeding, and multiplying stage of a protozoan parasite that causes disease inside a host

cyst

dormant, thick-walled, and resistant stage of a protozoan parasite that survives outside of the host (harsh environments) and spreads infection

What life stage do most protozoa infect humans at?

protozoa infect humans in the cyst phase (usually through fecal-oral contamination) and cause human disease in the trophozoite stage (once inside the body)

helminth

large, multicellular worms

a type of parasite that can infect humans

eggs and larvae are microscopic but the adult stage can be seen w/out magnification

2 body types: flatworms + roundworms

roundworms

also called nematodes

cylindrical body shape

usually infect the human gastrointestinal tract

2 types of flatworms

1) cestodes (tapeworms): long, ribbonlike, segmented worms; usually infect the gastrointestinal tract

2) trematodes (flukes): flat, ovoid bodies that can infect many human tissues

scolex

tapeworm (cestode) mouth parts

hooks are used to attach the tapeworm to the intestinal tract and the suckers are used to feed off the tissue

proglottid

tapeworm segments; can be full of eggs

ventral sucker

fluke attachment part that suction cups to the tissue; prevents detachment

cuticle

outer layer of roundworms that functions as protection

What are the life cycle stages for most helminths?

3 stages:

1) fertilized egg

2) larval

3) adult

infection of humans usually occurs in the egg or larval stage

pathogenesis (disease progression in an organism) occurs in the adult stage

What is the difference between an intermediate and definitive

host?

intermediate (secondary) host: host in which the larval development occurs

definitive (final) host: host in which the adulthood and mating occur

Do worms use sexual or asexual reproduction?

reproduce sexually in the host’s body

acellular

refers to something that lacks a cellular structure (lack cell membranes, cytoplasm, ribosomes)

usually made up of proteins, nucleic acids, lipids, carbohydrates, etc.

acellular pathogens

infectious agents that don’t have a cellular structure

ex: viruses and prions

relative scale of microbes

helminths > fungi > protozoa > bacteria > viruses > prions

What are the 3 essential components of a virus?

1) genome

2) capsid

3) viral attachment proteins

viral attachment proteins

bind specifically to host receptor proteins

functions: attachment and entry

each viral species has a unique viral attachment protein

determines tropism: which cells can be infected by a virus

capsid

protects the genome from damage

can be helical (rod-shaped), icosahedral (spherical), or complex (irregular shape)

What is the purpose of an envelope? Do all viruses have

this?

envelope is made up of a host cell membrane functioning to protect and disguise the virus from the host immune system

not all viruses have envelopes (naked)

genome

total genetic material of a virus (DNA or RNA) packed inside the protective capsid

negative sense RNA (complementary to mRNA that must be transcribed before translation) or positive sense RNA (acts directly as mRNA for protein translation)

What else might viruses carry into the cell with them?

enzymes or other proteins

polymerases for replicating nucleic acids

• RNA Dependent RNA Polymerase (RDRP) to translate RNA to RNA

• reverse transcriptase (RT) to convert RNA to DNA