> See also: > - [[Microbiomes]] > - [[Bacteria]] ![[e.-coli-gif.webp]] https://microbenotes.com/ # Microbiology Only about 3% of microorganisms cause harm/disease, the rest are harmless or even are necessary for our bodies to function. Microorganisms play a major role in the recycling of essential elements (carbon, nitrogen, oxygen, etc) [[History of Microbiology]] [[Microscopy]] All living organisms must have a **cell membrane** Cellular () - Ex: Fungi Fungi & Protists are Eukaryotes Bacteria & Archaea are Prokaryotes --- **Acellular** microorganisms lack a cell wall, - Ex: Viruses, Viroids, Sattelites, Prions One of the earliest classification schemes was a three-domain system The presence of 16S & 18S rRNA (components of the ribosomal subunits) were used for the classification of microorganisms Viroids are composed solely of RNA folded into a complex structure Many prions are caused by excess beta sheets within the protein, preventing it from folding properly and achieving its secondary structure. Last Universal Common Ancestor (LUCA) Because prokaryotes only contain one copy of their genetic information, and mutations that occur will result in some change to the cell’s function - *Asexual reproducing* cells can undergo **horizontal gene transfer** events (bacteriophages, conjugation between bacteria) ## Microbial Species > See also: > - [[Taxonomy]] > Genus > Species > Strain A species Strains of microorganisms have descended from a single progenitor and can be differentiated by their variations: - *biovars*: differ biochemically and physiologically - *morphovars*: differ morphologically (shape) - *serovars*: differ in antigenic properties (require different antibodies) A **type strain** is the *first strain that was studied*, regardless of its place in the timeline/tree of the species. [[Cells]]