Microbiology Flashcards
What are the domains of life?
- eubacteria /prokaryotes
- eukaryotes
- archea
What are the major groups of human pathogens?
Protozoa, fungi, bacteria, viruses
What are Protozoa?
Single called animals (eukaryotes)
What are fungi?
Higher plant like organisms (eukaryotes)
What are bacteria?
Generally small, single celled prokaryotes
What are viruses?
Very small obligate parasites (non-living)
Describe features of eukaryotes
- larger in size than prokaryotes (5-50mm)
- complex (compartmentalise)
- frequently multi-cellular
- linear chromosomes + histones
- introns/exons
- 80s ribosomes
- no/ flexible cell wall
- cell cycle includes meiosis and mitosis
Describe the features of prokaryotes
- relatively smaller than eukaryotes (0.5-10mms)
- simple
- often single celled
- single circular chromosome
- introns are rare
- 70s ribosomes
- co-transcription/ translation
- rigid cell walls (PG)
- rapid cell cycle
Describe nucleotides (in bacteria)
- they have no nuclear membrane
- contains DNA and proteins
- chromosomes are single circular molecules
- primitive DNA segregation machinery
Describe the features of the cytoplasmic membrane
- electrons are released from high energy compounds in cytoplasm
- reach membrane and passed through a series of electron acceptors
- as a consequence protons passed outside the membrane producing a positive charge and proton gradient across the membrane
Describe the features of the cell wall
- Made of Peptidoglycan (NAM and NAG)
- rigid layer and barrier formed from a repeated polysaccharide structure.
- target of penicillin
- can be gram positive (thick multilayer PG) or gram negative (outer membrane, periplasm and thinner PG layer)
Describe the features of lipopolysaccharide (LPS)
- gram negative (outer membrane is asymmetric, surface nearly all LPS)
- glycolipid
- lipid molecule attached to a polysaccharide
It has a structural role and is an antigen and bacterial toxin.
What are flagella and what are the features?
Long whip like structures which help some single celled organisms move.
Can be gram positive or negative
Are made up of flagellin (protein unit) making a multi stranded filament with core.
What are fimbriae?
Gram positive non-flagella protein appendages.
Thinner and shorter than flagellum
What are pilus?
Hair-like appendages found on the surface of many bacteria and archea.
Pilus have no motor and are composed of the pilin repeating unit.
Length, number, arrangement, shape and function can vary
Describe prokaryotic protein synthesis
- Has distinct proteins
- involves co-transcription/translation
- occurs in cytoplasmic membrane
- no polyadenylation of transcript
- target for antibiotics
What basic structures can be found in prokaryotes?
cytoplasm, plasma membrane, cell wall, outer membrane, LPS, chromosome, ribosome, pili, fimbriae, flagella
What is required for prokaryotic growth?
- food and nutrition
- appropriate temperature
- appropriate hydrogen ion conc.
- osmotic protection
- appropriate oxygen conc.
What are the growth phases of bacteria?
Lag, exponential /log, stationary, decline
How do most bacteria live?
In large communities
What are the common shapes of bacteria?
Cocci (spheres), bacilli (rods), spiral shaped, fusiform (elongated slender), vibrio (slightly curved rods)
Describe coccus/cocci
Division in one plane produces two cocci eventually resulting in a chain (eg streptococcus)
Division in three planes results in clumps (staphylococcus)
(Spheres)
Describe bacilli
(Rodshaped)
Makes chains of bacilli
Describe vibrio
Slightly curved rod
Gram negative