All cells have 3 main components: Nucleoid a region where DNA is located Plasma membrane limits access to the cell‟s interior Cytoplasm a place where all metabolic reactions occur(e.g. protein synthesis, which occurs on theribosomes) a gel-like structure composed mainly of water thatcontains enzymes, salts, cell components, andorganic molecules
Bacteria also often have these features: Cell wall helps the cell retain its shape made of peptidoglycan Flagellum plural: flagella responsible for movement Pili are filamentous proteins that help cellsadhere to a surface or facilitate conjugation
Glycocalyx sometimes called „capsule‟ a sticky layer composed of proteins orpolysaccharides that surround the cell wall for protection Plasmid circles of DNA apart from the nucleoid Ribosome site for protein synthesis
Prokaryotes reproduce by BINARY FISSION,an asexual process that replicates DNA anddistributes it and other cell parts into twodaughter cells.
Binary fission is an effective way for bacteria toreproduce, however it does produce problems. Sincethe cells produced through this type of reproductionare identical, they are all susceptible to the same typesof antibiotics. In order to incorporate some geneticvariation, bacteria use a process called recombination. Bacterial recombination can be accomplished throughconjugation, transformation, or transduction.
one bacterium connectsitself to another througha protein tube structurecalled pilus or sex pilus.Genes are transferredfrom one bacterium tothe other through thistube. sometimes called“bacterial sex”
a prokaryote takes up naked DNA withoutcell-to-cell contact. It occurs when prokaryotesdie and pieces of their DNA enter other cells.
It is a type of recombination that involves theexchanging of bacterial DNA throughbacteriophages.
Bacteria are present in almost everyenvironment, e.g. in the soil, in the air, inanimals and plants. They are found all over ourbodies e.g. on our skin, in our mouth and inour gut. Most are harmless and are evenbeneficial.
Nutrition refers to how an organism obtainsenergy and a carbon source. Phototrophs arespecies that use light energy, and chemotrophsobtain their energy from chemicals taken fromthe surrounding environment. An autotroph isan organism that only needs carbon dioxide asits carbon source, and a heterotroph is anorganism that requires at least one organicnutrient as a source of carbon for making otherorganic compounds.
The four major modes of nutrition for prokaryotes are:1. Photoautotrophs are photosynthetic organisms thatharness light energy to drive the synthesis of organiccompounds from carbon dioxide. All photosyntheticprokaryotes use this mode of nutrition.2. Chemoautotrophs only require carbon dioxide as acarbon source. Instead of using light for energy, theyobtain energy by oxidizing inorganic substances. Onlycertain prokaryotes use this mode of nutrition.3. Photoheterotrophs may use light to make ATP butmust also obtain carbon in organic form. Only certainprokaryotes use this type of nutrition.4. Chemoheterotrophs consume organic molecules forenergy and carbon.Prokaryotes, protists, fungi, animals and some plantsuse this nutritional mode.
Most bacteria are heterotrophic, living off otherorganisms. Most of these are saprobes, bacteriathat live off dead organic matter. The bacteria thatcause disease are heterotrophic parasites. There arealso many non-disease-causing bacterialparasites, many of which are helpful to their hosts. Autotrophic bacteria manufacture their own foodby the processes of photosynthesis andchemosynthesis (see autotroph ). Thephotosynthetic bacteria include the green andpurple bacteria and the cyanobacteria . Many ofthe thermophilic archaebacteria arechemosynthetic autotrophs.