Microbial ecology

Source: Wikipedia, the free encyclopedia.

The great plate count anomaly. Counts of cells obtained via cultivation are orders of magnitude lower than those directly observed under the microscope. This is because microbiologists are able to cultivate only a minority of naturally occurring microbes using current laboratory techniques, depending on the environment.[1]

Microbial ecology (or environmental microbiology) is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life—Eukaryota, Archaea, and Bacteria—as well as viruses.[2]

Microorganisms, by their omnipresence, impact the entire

sulphur metabolism) control global biogeochemical cycling.[9] The immensity of microorganisms' production is such that, even in the total absence of eukaryotic life, these processes would likely continue unchanged.[10]

History

While microbes have been studied since the seventeenth century, this research was from a primarily physiological perspective rather than an ecological one.

microorganisms outside of the medical context—making him among the first students of microbial ecology and environmental microbiology—discovering chemosynthesis, and developing the Winogradsky column in the process.[14]
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Beijerinck and Windogradsky, however, were focused on the physiology of microorganisms, not the microbial

Progress in microbial ecology has been tied to the development of new technologies. The measurement of biogeochemical process rates in nature was driven by the availability of radioisotopes beginning in the 1950s.  For example, 14CO2 allowed analysis of rates of photosynthesis in the ocean (ref). Another significant breakthrough came in the 1980s, when microelectrodes sensitive to chemical species like O2 were developed.[15] These electrodes have a spatial resolution of 50–100 μm, and have allowed analysis of spatial and temporal biogeochemical dynamics in microbial mats and sediments.[citation needed]

Although measuring biogeochemical process rates could analyse what processes were occurring, they were incomplete because they provided no information on which specific microbes were responsible. It was long known that 'classical' cultivation techniques recovered fewer than 1% of the microbes from a natural habitat. However, beginning in the 1990s, a set of cultivation-independent techniques have evolved to determine the relative abundance of microbes in a habitat. Carl Woese first demonstrated that the sequence of the 16S ribosomal RNA molecule could be used to analyse phylogenetic relationships.[16] Norm Pace took this seminal idea and applied it to analysfe 'who's there' in natural environments. The procedure involves (a) isolation of nucleic acids directly from a natural environment, (b) PCR amplification of small subunit rRNA gene sequences, (c) sequencing the amplicons, and (d) comparison of those sequences to a database of sequences from pure cultures and environmental DNA.[17] This has provided tremendous insights into the diversity present within microbial habitats. However, it does not resolve how to link specific microbes to their biogeochemical role. Metagenomics, the sequencing of total DNA recovered from an environment, can provide insights into biogeochemical potential,[18] whereas metatranscriptomics and metaproteomics can measure actual expression of genetic potential but remains more technically difficult.[19]

Roles

Microorganisms are the backbone of all

chemosynthetic microbes provide energy and carbon to the other organisms. These chemotrophic organisms can also function in environments lacking oxygen by using other electron acceptors for their respiration.[citation needed
]

Other microbes are

nitrogen gas which makes up 78% of the Earth's atmosphere is unavailable to most organisms, until it is converted to a biologically available form by the microbial process of nitrogen fixation.[22] Differing from the nitrogen and carbon cycles, stable gaseous species are not created in the phosphorus cycle in the environment. Microorganisms play a role in solubilizing phosphate, improving soil health and plant growth.[23]

Due to the high level of horizontal gene transfer among microbial communities,[24] microbial ecology is also of importance to studies of evolution.[25]

Evolution

Microbial ecology contributes to the evolution in many different parts of the world. For example, different microbial species evolved CRISPR dynamics and functions, allowing a better understanding of human health.[26]

Symbiosis

Microbes, especially bacteria, often engage in symbiotic relationships (either positive or negative) with other microorganisms or larger organisms. Although physically small, symbiotic relationships amongst microbes are significant in eukaryotic processes and their evolution.[27][28] The types of symbiotic relationship that microbes participate in include mutualism, commensalism, parasitism,[29] and amensalism[30] which affect the ecosystem in many ways.

Mutualism

Mutualism in microbial ecology is a relationship between microbial species and humans that allows for both sides to benefit.

sulfate-reducing bacterium and an anaerobic methane-oxidizing archaeon.[36][37] The reaction used by the bacterial partner for the production of H2 is endergonic (and so thermodynamically unfavored) however, when coupled to the reaction used by archaeal partner, the overall reaction becomes exergonic.[27]  Thus the two organisms are in a mutualistic relationship which allows them to grow and thrive in an environment, deadly for either species alone. Lichen is an example of a symbiotic organism.[33]

Commensalism

Commensalism is very common in microbial world, literally meaning "eating from the same table".[38] Metabolic products of one microbial population are used by another microbial population without either gain or harm for the first population. There are many "pairs "of microbial species that perform either oxidation or reduction reaction to the same chemical equation. For example, methanogens produce methane by reducing CO2 to CH4, while methanotrophs oxidise methane back to CO2.[39]

Amensalism

Lactobacillus casei and Pseudomonas taetrolens.[40] When co-existing in an environment, Pseudomonas taetrolens shows inhibited growth and decreased production of lactobionic acid (its main product) most likely due to the byproducts created by Lactobacillus casei during its production of lactic acid.[41] However, Lactobacillus casei shows no difference in its behaviour, and such this relationship can be defined as amensalism.[citation needed
]

Microbial resource management

antibiotic resistance, a pressing concern for researchers.[43]

In built environment and human interaction

Microbes exist in all areas, including homes, offices, commercial centers, and hospitals. In 2016, the journal Microbiome published a collection of various works studying the microbial ecology of the built environment.[44]

A 2006 study of pathogenic bacteria in hospitals found that their ability to survive varied by the type, with some surviving for only a few days while others survived for months.[45]

The lifespan of microbes in the home varies similarly. Generally bacteria and viruses require a wet environment with a humidity of over 10 percent.[46] E. coli can survive for a few hours to a day.[46] Bacteria which form spores can survive longer, with Staphylococcus aureus surviving potentially for weeks or, in the case of Bacillus anthracis, years.[46]

In the home, pets can be carriers of bacteria; for example, reptiles are commonly carriers of salmonella.[47]

S. aureus is particularly common, and asymptomatically colonizes about 30% of the human population;[48] attempts to decolonize carriers have met with limited success[49] and generally involve mupirocin nasally and chlorhexidine washing, potentially along with vancomycin and cotrimoxazole to address intestinal and urinary tract infections.[50]

Antimicrobials

Some metals, particularly copper, silver, and gold have antimicrobial properties. Using antimicrobial copper-alloy touch surfaces is a technique which has begun to be used in the 21st century to prevent transmission of bacteria.[51][52] Silver nanoparticles have also begun to be incorporated into building surfaces and fabrics, although concerns have been raised about the potential side-effects of the tiny particles on human health.[53] Due to the antimicrobial properties certain metals possess, products such as medical devices are made using those metals.[52]

See also

References

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