The main aim of this study is to know how microorganisms(especially bacteria)interact with human beings.At some point in this essay,it would discuss; the structure and function of different types of microorganisms, how these organisms are studied in the laboratory, factors affecting the growth, survival and death of microorganisms, how microorganisms can be classified based on their nutritional carbon source, phases of bacterial growth in relation to the growth curves, how bacteria causes food spoilage and the last but not the least,some examples of positive and negative microbe-human interactions referring to specific bacteria.
Microorganisms can be grouped into seven types: bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites (helminths). Research has shown that taxonomy consists of three components which includes; classification, nomenclature and identification. Classification allows the orderly grouping of micro-organisms, though nomenclature concerns the naming of these organisms and requires agreement so that the same name is used unequivocally by everybody.Cells are classified as prokaryotes or eukaryotes.Organisms whose cells contain a nucleus are called Eukaryotes ,and those cells that lack a nucleus and have no membrane-bound organelles are known as Prokaryotes.Prokaryotes include the kingdoms of Monera(simple bacteria)and Archaea. Prokaryotic cells may have photosynthetic pigments,such as is found in cyanobacteria(“blue bacteria”).Eukaryotic cell have structures that are determined by the specific functions carried out by the cell.They generally have three main components;a cell membrane,nucleus,and a variety of other organelles.
Bacteria are similarly classified, but bacterial diversity encompasses more variety than all the rest of cellular life put together and the natural capacity of bacteria for genetic and phenotypic variation and adaptation make rigid classifications difficult. To date, identification has predominantly been performed by the use of keys that allow the organization of bacterial traits based on growth or activity in systems that test their biochemical properties. The taxonomic ranks used in the classification of bacteria are (example in brackets):Kingdom(Prokaryotae),Division(Gracilicutes),Class (Betaproteobacteria),Order(Burkholderiales),Family (Burkholderiaceae),Genus(Burkholderia),Species(Burkholderia cepacia).(T.L.Pitt,M.R.Barer 2012,p.24-28)
A population of bacteria grown in the laboratory is referred to as a culture. A pure culture contains only one single type of organism,getting a pure culture of bacteria is usually accomplished by spreading bacteria on the surface of a solid medium so that a single cell occupies an isolated portion of the agar surface. This single cell will go through repeated multiplication to produce a visible colony of similar cells, or clones; a mixed culture contains two or more different organisms(viruses,bacteria,and parasites) that grows in a sterile medium and share the available resources. If a bacterial culture is left in the same media for too long, the cells use up the available nutrients,they will also excrete toxic metabolites, and the entire population might perish. Thus bacterial cultures must be sporadically transferred, or subcultured, to a new media to keep the bacterial population growing.
Some factors that affect the growth and death of organisms are nutrients, temperatue and pH level;Nutrients are essential for microorganisms,and these microorganisms basically get carbon and nitrogen from substances like the Macromolecules (protein,fats and carbohydrates),some microorganisms carry out a chemical reaction with the elements surrounding them to get what is essential for their growth,example is carbon dioxide.So if organisms are unable to get the necessary nutrients needed for survival,they will eventually die or break down. Most organisms can not survive without living in a certain temperature,that is,some organisms can grow up to certain level with a very high or low temperature.Some organisms prefer 0 to 5 degrees Celsius and others may prefer to live in 55 degress Celsius and above. The pH is not left out as it one of the important factors,just as the temperature, some organisms prefer a pH to be in a particular level for them to survive. Some microorganisms will die if the pH scale is acidic. Some other factors include
- T.L.Pitt,M.R.Barer Medical Microbiology (Eighteenth Edition) 2012, Pages 24-3810.1016/B978-0-7020-4089-4.00018-4