week 1: introductory concepts in microbiology

microbes

aka: microorganisms, tiny living things too small to see

acellular infectious agents

prions, viruses

cellular microorganisms

• prokaryotes: archaea, bacteria

• eukaryotes: algae, fungi, protozoa

microbe is not a pathogen, but ___

it does when it becomes a disease/harmful

infection

includes microorganism in host; colonizes

intoxication

results from exposure to microbial toxin; in vitro: outside living host (food or external environment)

indigenous (resident) microbiota vs. opportunistic pathogen

indigenous microbiota → coexist with host → may cause disease when conditions change

what conditions support indigenous microbiota becoming opportunistic:

• different or normal sterile body site (ex: bladder free of microbes; if it is = problem)

• disrupted protective barrier (ex: skin breakdown)

• altered microbiota or overgrown (ex: colon has good bacteria; if take good + bad = bad outgrows = problem)

• weakened host defenses (ex: immunocompromised patient)

benefits and harmful roles of microorganisms:

• ecosystem: decomposition, nutrient cycling, food webs

• human body: microbiota, digestion, colonization resistance

• food & industry: fermentation, biotechnology

• medicine: antibiotics, vaccines, models of cells

microbe to microbe interaction

• antagonism: microbes vs microbes

• synergism: two or more microbes interact in ways that may increase their combined effects

microbes = microscopic

• human cell (~10-100 μm)

• bacterium (~1 μm)

• virus (~μm scale)

magnification

how much larger image appears; image = bigger

resolution

how clearly 2 close objects be seen as separate; image = fine details clearer

light microscopy

uses visible light + system of lenses to magnify and observe small species

electron microscopy

uses beam of electrons to view objects

• TEM: internal detail

• SEM: external detail, surfaces

prokaryotic cells

• no true nucleus

• non membrane-bound organelles

• smaller ribosomes

• ex: bacteria, archaea

• DNA present, not in true nucleus

• binary fission for reproduction

eukaryotic

• true nucleus present

• present membrane-bound organelles

• larger ribosomes

• ex: fungi, protoza, human cells

• DNA present in nucleus

• mitosis and meiosis for reproduction

cell membrane

• selective barrier (homeostasis)

• many bacteria generate ATP across cell membrane

• some antimicrobials disrupt the bacteria cell membrane (ex: daptomycin - antibiotic)

bacterial cell wall

• provides shape, protection, and structural integrity

• most ___ contain peptidoglycan

• ____ differences determine gram-stain reactions + some antimicrobials inhibit peptidoglycan synthesis, weakning the _________

cell walls: present vs absent

• present: plants, algae, fungi, most bacteria

• absent: animals, protozoa, mycoplasma species

capsule

• highly organized glycocalyx

• some ___ resist phagocytosis, help bacteria evade host defenses

• ex: klebsiella pneumonia, neisseria meningitidis, and streptococcus pneumoniae

chromosome

• DNA molecule, contains genetic information

• prokaryotic DNA has no nucleus

plasmid

• extrachromosomal DNA

• it may carry antimicrobial-resistance genes

flagella

for motility → colonization + pathogenesis

fimbriae

• allows bacteria to attach to surfaces (adhesion)

• not for motility

• adhesion → colonization

sxx pilus

• enable DNA transfer between bacteria during conjugation

• may spread antimicrobial resistance genes

endospore

highly resistant survival structure, not reproductive structures

• resist harsh environmental conditions + many disinfectants

• not a reproductive structure

• helps some bacteria persist in environment

• ex: bacillus spp., clostridium spp.

• **alcohol not work, need to use soap and water instead

slime layer

loosely attached glycocalyx (capsule = more organized)

• promotes surface attachent, contributes to biofilm formation → persistence on tissues and devices (ex: endotracheal tubes, urinary catheters, IV catheters)

• ex: pseudomonas aeruginosa

binary fission

parent cell; dna replication → cell divides → two daughter cells