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Microorganisms, or microbes, span all three domains of life – bacteria, archaea, and many unicellular eukaryotes including some fungi and protists.Typically defined as unicellular life forms that can only be observed with a microscope, microorganisms were the first cellular life forms, and were critical for creating the conditions for the evolution of more complex multicellular forms.
Consortia are commonly found in humans, with the predominant examples being the skin consortium and the intestinal consortium which provide protection and aid in human nutrition. Additionally, bacteria have been identified as existing within the brain (previously believed to be sterile), with metagenomic evidence suggesting the species found ...
[7] [8] The presence of microbiota in human and other metazoan guts has been critical for understanding the co-evolution between metazoans and bacteria. [ 9 ] [ 10 ] Microbiota play key roles in the intestinal immune and metabolic responses via their fermentation product ( short-chain fatty acid ), acetate .
A phenomenon called fratricide can be seen among streptococcal species in which cell-wall degrading enzymes are released, lysing neighboring bacteria and releasing their DNA. This DNA can then be taken up by the surviving bacteria (transformation). [ 171 ]
Graphic depicting the human skin microbiota, with relative prevalences of various classes of bacteria. The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, [1] [2] including the gastrointestinal tract, skin, mammary glands, seminal fluid, uterus, ovarian follicles, lung ...
The temperature and pH of saliva makes it conducive for bacteria to survive in the oral cavity. Bacteria in the oral cavity include Streptococcus mutans, Porphyromonas gingivalis, and Staphylococcus. [15] S. mutans is the main component of the oral microbiota. [15] A healthy oral microbiome decreases oral infections and promotes a healthy gut ...
Access to the previously invisible world opened the eyes and the minds of the researchers of the seventeenth century. Antonie van Leeuwenhoek investigated diverse bacteria of various shapes, fungi, and protozoa, which he called animalcules, mainly from water, mud, and dental plaque samples, and discovered biofilms as a first indication of microorganisms interacting within complex communities.
Many bacteria secrete extracellular polymers outside of their cell walls called glycocalyx. These polymers are usually composed of polysaccharides and sometimes protein. Capsules are relatively impermeable structures that cannot be stained with dyes such as India ink. They are structures that help protect bacteria from phagocytosis and desiccation.