Methanogens produce methane from simple carbon compunds. Live in O2-less sewage, swamps, digestive tracts of humans and animals. Extreme halophiles live in high salt ponds. Purple pigment rhodopsin uses sun energy, but different from photosynthesis. Fix nitrogen from atmosphereic N2 to nitrates, which plants use for proteins and nucleic acids.
Bacterial photosynthesis is half the primary productivity in aquatic habitats.
Cyanobacteria use water as electron source, others use H2S and don t produce O2. Prevents harmful bacteria from growing, make vitamins, etc Opportunistic pathogens are normally present and harmless in body, but can cause problems if immune system isn t working right. Pathogens come in through food, water, dust, wounds, bug bites. Adheres to specific cell type, multiply and produce toxic substances. Exotoxins are secreted or leak from cells when destroyed.