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Are we human, or are we…
The diversity of microbes
Diversity of MicrobesMicrobes are ubiquitous on our
planet◦Found in every environment
imaginable50% of all biomass is thought to
be made up of microbesBacteria and other microbes help
our world function as we know it◦Fermentation nitrogen fixation◦Biopharmaceuticals decomposition◦Digestion food production
Diversity of Microbes
1 trillion vs 10 trillion30k genes vs 30 million
Diversity of Microbes5 Kingdoms system has been used since
1959Grouping stated with Linnaeus (1700s)
Can be grouped into eukaryotes and prokaryotes
Late ‘80s Carl Woese used rRNA to identify differences in prokaryotes
Led to a new classification system, the 3 Domains
Diversity of MicrobesThe 3 Domains are:
◦ Eubacteria: typical prokaryotes◦ Archaea: extremophiles
◦ Eukarya: single and multicellular organisms with a membrane bound nucleus
5 kingdoms based on structural differences, 3 Domains molecular differences
Variations in rRNA sequences led to a clear distinction within the three domains and provided another evolutionary piece of evidence
Be familiar with the table on page 514
Diversity of MicrobesThe split into the 3 domains was
really to help explain discrepancies that were seen within the 5 kingdoms
Each of the 5 kingdoms would fit within one of the three domains
Main problem archaea were classified within the same kingdom as bacteria◦Molecularly more closely related to
eukaryotes (all based on rRNA structures)
Diversity of Microbes--ArchaeaThese are the extremophiles—
they live in very harsh conditionsThese conditions are thought to
be similar to life on early EarthThey can split into three main
groups:◦Methanogens—used CO2 to produce
CH4
◦Thermophiles—heat loving, usually acidic
◦Halophiles—salt loving, 10x greater than oceans
Diversity of Microbes--BacteriaTypically found in arrangements with three
different shapes◦ Spherical (cocci)◦ Rods (bacilli)◦ Helices (spirilla)
Can occur as single cells or groups of cells◦ Staphylococcus—bunch of spheres◦ Streptococcus—chain of spheres◦ Diplococcus—pair of spheres
These arrangements are used in part to identify bacteria
Diversity of Microbes--BacteriaBesides shape, one major way to
differentiate between bacteria is cell wall morphology
Gram staining is an easy way to differentiate between these differences
Gram (+) Gram (-)
Purple Pink
Lots of peptidoglycan Little peptidoglycan
No outer membrane Outer membrane
More susceptible to antibiotics
Less susceptible to antibiotics
Diversity of Microbes--BacteriaBacteria have a way in which they can
communicate with one another◦ Quorum sensing relies on chemical signals
Not all QS is cool…most pathogenic microbes also use QS to release toxins that cause illness
Diversity of Microbes--VirusesViruses are not alive, but still
considered microbesCome in a variety of shapes and with
multiple methods of replicatingSame general packaging regardless of
type of virus◦ Protein coat (encapsulated or not)◦ Nucleic acid (ssDNA/RNA or dsDNA/RNA)◦ Internal enzymes
Diversity of Microbes-eukaryotes
Not all microbes are prokaryotes
MEMBRANE BOUND NUCLEUS
YEASTFermentation alcohol and CO2
AMOEBAPseudopodia & food
vacuoles (intracellular digestion)
PLASMODIAParasitic heterotrophs
PARAMECIUMCiliate heterotrophs; food vacuole + lytic
enzymes vacuole
EUGLENAHeteroautotrophs,
chlorophyll and photoreceptors
CHLORELLASingle celled green algae
Chlorphyll, non-motile, cellulose
Diversity of MicrobesThe world around you functions as a result
of microbes in ways which we usually don’t recognize
Two good examples of this would be the Nitrogen Cycle and Waste Water Treatment
Section F.2 in the book discusses microbes in the environment, be sure to know the details from that section
With all these examples, the natural metabolism of microbes is used in some way to benefit us
Diversity of MicrobesMicrobes can be producers, decomposers,
and nitrogen fixers“fixing” a gas simply takes it from a gaseous
state to a form which can be used by organisms
The nitrogen cycle is responsible for taking nitrogenous wastes from plants and animals and turning it into nitrogen gas (N2)
It is also responsible for taking nitrogen gas and converting it into nitrates, nitrites, and ammonia which can be used metabolically by plants which are then consumed by animals
Diversity of MicrobesAMMONIA
NH3
Gaseous NitrogenN2
1
NITRATES/NITRITES
2
3
4
5
6
7
1) Fixation 2) Nitrification 3) active transport of Nitrate ions 4) consumption 5) death and excretion 6) putrefaction 7) denitrification
Diversity of MicrobesWhat happens to the water in your toilet
after you flush?◦ How would you feel knowing that it will be
recycled and you could drink it later?It’s because of microbes, specifically
saprotrophs, that this is possibleWater from bath tubs, showers, toilets,
washing machines, dishwashers, and business and industry all sent to treatment plants
Water is treated and eventually reused◦ Solid wastes are removed (in inorganic), consumed (by
microbes), and concentrated and sent to a landfill (sludge)
Diversity of Microbes
Diversity of MicrobesMany food production processes require
microbesBeer, wine, bread, sauerkraut/kimchi, yogurt,
and soy sauce are all produced using microbes◦ Make sure you can explain the production of soy sauce by using Aspergillus
oryzae
Processes are also in place to preserve food to prevent spoilage by microbes◦ Canning/Pickling – uses pH (acids) and salt to
prevent spoiling
◦ Preserves—uses high sugar concentration
◦ Pasteurization—uses heat and a sealed environment
Diversity of MicrobesFood poisoning can occur if preservation
techniques are done poorly or if fresh food is left to spoil
Salmonella infections are common food-borne illnesses
Studies have shown 80% or more of chicken at grocery stores are contaminated
Fully cooking food will prevent illnessMost infections result from undercooked
food, irrigation with contaminated water, or cross-contamination
Diversity of MicrobesWith salmonellosis symptoms (cramps,
diarrhea, fever) will develop 12 to 72 hours after infection
Severe dehydration can result in hospitalization
Without treatment, infection can spread to blood and lead to death (not typical)
Antibiotics will take care of the infectionTo fully diagnose salmonellosis fecal samples
must be tested for the presence of the bacterium
~40,000 cases reported in the U.S. each year
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