Monotrichous= 1 flagella Lophotrichous= multiple flagella in the same area Amphitrichous= 2 flagella; the flagella are on opposite ends of the cell Peritrichous= multiple flagella pointing in many directions/located at many spots on the cell.
Bacteria cell structure and function
Cell structure and function for microbiologistsProkaryotesEukaryotesBoth have the same types of biologicalmolecules metabolism, protein synthesis, ATP
Eukaryotes have organelles Much larger; more complex than prokaryotes Processes compartmentalized into organelles Nucleus Protein synthesis (ribosomes, RER, Golgi) Mitochondria; chloroplasts Lysosomes Plasma membranes have different modifications Cytoskeleton
Eukaryotes may be multicellular Cells may be variable within the organism Tissues Organs
Prokaryotes:Have no nucleus; genome is circularNo histonesNo membrane-bound organellesCell wall usually contains peptidoglycan (cell walls are more complex)Divide by binary fission
Prokaryotes include eubacteria and archaeHow do you tell them apart? They’re all small! morphology chemical composition nutritional and energy requirements
Typical shapes of bacteriaMost bacteria retain a particular shape; a few are pleiomorphic
Even in groups, bacteria tend to be single- celled in structure and behaviorSome have “colonial” traitsWell-studied example: myxobacteria “hunting” colonies fruiting bodiesEtc.
Typical prokaryotic structuresWorking from the outside in…
Extracellular componentsProtection dehydration immune mechanismsAttachmentGlycocalyx- polysaccharide, protein capsule if organized slime layer if notMay contribute to virulence
Some bacteria are motile (due to flagella)Bacteria vary in the way flagella are attachedHow they move: running, tumbling, swarmingCan move toward or away from light or chemical stimuliFlagellin protein is unique to prokaryotes
Cocci do not have flagellaPeritrichous monotrichous(or amphi, or lophotrichous
Cell membrane structure is similar in structure and function to that of eukaryotesPhospholipid bilayer (everything moves through it, since there are no organelles) carrier proteins generally involve proton motive force (i.e, require energy and moving against the concentration gradient)
Cell wall- hallmark of prokaryotesTheir reaction with Gram stain allows bacteria to be divided into two groupsPositive-lots of peptidoglycanNegative- thin layer, with an outer membrane and “periplasmic space” in between Many secreted proteins are found here
Outer membrane is made of lipopolysaccharide (LPS)Porins allow molecules to pass through outer membraneLPS is protective lipid A- strong inflammatory response (endotoxin) O-linked polysaccharide- antigenic
Significance of Gram-positive vs Gram-negative antibiotic sensitivity sensitivity to lysozyme reaction with Gram reagents crystal violet iodine alcohol safranin
Mycoplasma do not have a cell wallLots of variety in Achaea- but none have peptidoglycan
Internal componentsNucleoid- with single, circular, supercoiled DNA moleculeMany bacteria have plasmids small, extrachromosomal, circular piece of DNA genes present are usually not required but may be advantageous(antibiotic resistance, resistance to metals)Now used for genetic engineering
RibosomesInvolved in protein synthesisProkaryotic ribosomes are smaller than eukaryotic (70S vs 80S)Some antibiotics bind to the 70S ribosomeHow does that affect bacteria?
No membrane-bound organellesSome have storage granulesSome aquatic bacteria have gas vesiclesSome have endospores (soil bacteria) that enable them to lie dormant under “unfavorable” conditionsNOT a reproductive structure
Summary Eukaryotes have membrane-bound organelles Eukaryotes may be multicellular with highly specialized cells Prokaryotes have simple shapes and are classified according to their morphology Certain structures are unique to prokaryotes