Ch 2: Microbial Cell Structure & Function
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3 usual cell shapes in microbes
• coccus • rod • spirillum
3 unusual cell shapes in microbes
• spirochete • budding and appendaged bacteria • filamentous bacteria
what are characteristic arrangements in cells
cells remain in groups and clusters even after cell division in characteristic arrangement that can assist in identification
different ways of cell arrangement examples
• cocci in chains • cocci in clusters • rods in chains
what is morphology
genetically encoded property that maximizes fitness in a particular habitat
how can morphology maximize fitness
• optimization of nutrient uptake • swimming motility in viscous environments of near surfaces • gliding motility (like filamentous bacteria
Can the morphology predict physiology, ecology or phylogeny of a cell
typically, no
what is the size range for prokaryotes
~0.2um – 700 um in diameter
size of the average rod in bacteria
2 um
what is the size of most eukaryotes
8 um or larger
examples of very large prokaryotes
• Epulopiscium fishelsoni (bigger than 600 um) • thiomargarita namibeinsis (400-750 um)
how does thiomargarita magnifica survive
by oxidixing sulfur. They are thread like creatures that are 50 times bigger than any other known bacteria
Small cells have more _______ relative to cell volume than large cell
surface area
core difference between small and large cell
the high surface are to volume ratio
what are the benefits of a large surface area
• support greater nutrient exchange • grow faster than large cells
Limited resources can work out for small cells or large cells
small. a large population of small cells can be taken care of, compared to large population of large cells
What are the benefits of having more cell division, which is easier in small cells
more cell divisions = more mutations = faster evolution
In cells that really small, what should the volume of a cell consist of
proteins, nucleic acids, ribosomes etc - so it may get difficult
what cell size are needed on a minimum
0.15 um is marginal. 0.1 is insufficient
usually cell size in open oceans
0.2 - 0.4 um in diameter
what is the size of pathogenic bacteria
very small.
If pathogenic bacteria are small, how do they accommodate all cell functions
their genomes are streamlined with some gene functions provided by hosts
what is the cytoplasmic membrane
a thin structure that surrounds the cytoplasm and separates it from the environment
what does the cytoplasmic membrane do
regulates traffic of substances into and out of the cell