NITROSOCOCCUS STREPTOCOCCUS LACTIS Based on their need for oxygen, bacteria are grouped into: • Obligate aerobic bacteria namely bacteria that can only live in an atmosphere containing oxygen. Example:Nitrobacter And Hydrogenomonas. • Obligate anaerobic bacteria namely bacteria that can only live in an atmosphere without oxygen. Example:Clostridium tetani. • Faculative anaerobic bacteria namely bacteria that can live with or without oxygen. Example:Escherichia coli,Salmonella thyposeAndShigella.Based on how they obtain food, bacteria can be classified into two groups, namely: 1.Heterotrophic bacteria 2.Autotrophic bacteria 1) Hetorotophic bacteria These bacteria live by obtaining food in the form of organic substances from their environment because they cannot prepare the organic substances they need themselves. a. Heterotrophic bacteria that are saprophytic Bacteria that obtain organic substances from garbage, feces, carcasses and also food waste. • These bacteria break down organic substances in food into inorganic substances, namely CO2, H2O, energy and minerals. • In the environment, these putrefactive bacteria function as decomposers and provide nutrients for plants. • Meanwhile, in the human intestine there are also bacteria that live saprophytically (break down the fibers in food) and beneficial bacteriaEscherichia coli. b. Heterotrophic bacteria that are parasitic These bacteria are detrimental to humans, animals and plants. These bacteria cause illness (pathogens). 2) Autotrophic bacteria • Autotrophic bacteria are bacteria that can make their own food from existing inorganic substances. • Based on the energy source they use, autotrophic bacteria (auto = self, trophein = food) are divided into two groups, namely: photoautotrophic bacteria and chemoautotrophic bacteria. a.Photoautotrophic bacteria namely bacteria that use light as energy to convert inorganic substances into organic substances through the process of photosynthesis. Example: green bacteria, purple bacteria. b.Chemoautotrophic bacteria namely bacteria that use the chemical energy they obtain when chemical substances are converted from complex molecules into simple molecules by releasing hydrogen.Example :Nitrosomonas, Nitrosococcus, Nitrobacter,Rhizobium