Microbiology is the study of microorganisms that are usually too small to be visible with the human eye without a microscope. Microorganisms also known as microbes are essential to life on Earth; complex organisms including human beings would find it nearly impossible to survive without them.
These tiny organisms shape how nutrients move through the environment, controlling how ecosystems work. For instance, they are responsible for how biological materials break down and decay. Microorganisms affect our climate, determine how food spoils, and both cause and control diseases.
We can also use microorganisms to help us produce life-saving drugs, manufacture biofuels , clean up pollution, and grow crops. Microorganisms can be unicellular single cell , multicellular cell colony , or acellular lacking cells. They include bacteria, archaea, fungi, protozoa, algae, and viruses.
The Department of Energy DOE supports microbiology research that helps us maintain energy security and a sustainable environment. The DOE Biological and Environmental Research BER program supports scientific research and facilities that seek to understand complex biological, earth, and environmental systems. Beyond research funded at academic institutions and national laboratories, DOE BER supports two facilities that conduct microbiology research.
It is understandably very difficult to comprehend that the human body, just a fraction of the size of our planet, is a world in its own right, housing trillion microbes in the gut alone. The human microbiota benefits from a rich and continuous supply of nutrients from the human host and in return, the resident microorganisms contribute greatly to human physiology. The fact that such a mutualistic relationship occurs suggests that the benefits that these microorganisms bring to the host do indeed outweigh any potential pathogenic threat.
This essay will discuss the vast advantages brought about by the microorganisms that live within us. The human gastrointestinal tract is home to a complex microbial community that is characterised by its extensive diversity and complex interactions.
The gastrointestinal microbiota consists largely of bacteria and it is predicted that bacterial species coexist in the gastrointestinal tract. Whereas humans do not possess the enzymes needed to digest certain dietary carbohydrates, some bacterial species are able to secrete the enzymes needed to break down these otherwise non-digestible substances, converting them into short chain fatty acids SCFAs.
Acetate, propionate and butyrate passively diffuse across the colonic epithelium and are then utilised by various different organs. Without this energy source, colonocytes would undergo autophagy and die. Butyrate is perhaps most famously known for protecting against colorectal cancer.
In a study, mice were colonised by mutant strains of the butyrate-producing bacterium, Butyrivibrio fibrisolvens. The mice showed an increase in colonic levels of butyrate and simultaneously, they developed fewer and less advanced colon tumours than those produced in mice lacking the bacterium. Tumour analysis of these mice showed greater expression of pro-apoptotic genes and a subsequent elevation in apoptotic markers in comparison to the control mice and the mice lacking the bacterium.
Acetate is the most abundant SCFA in the human body and is used in cholesterol metabolism and lipogenesis. In fact, acetate has been shown to make a larger carbon contribution to lipids than both propionate and butyrate.
The SCFA is further believed to act as a vital metabolite in the growth of other bacteria. Propionate, on the other hand, is a significant hepatic gluconeogenic substrate and unlike acetate and butyrate, contributes carbon atoms directly to the synthesis of glucose.
Gluconeogenesis GNG is a metabolic pathway that synthesises glucose or glycogen from certain non-carbohydrate organic substrates, supplying the need for plasma glucose in between meals. As well as stimulating gluconeogenesis, this SCFA has been linked to reduced stress behaviours.
Vitamins are inorganic compounds that are essential for the maintenance of good health and metabolism. Just as the human body does not have the enzymes needed to digest certain carbohydrates into SCFAs, humans do not have the enzymes needed to synthesise all the required vitamins.
For the vitamins that humans can indeed synthesise, they are generally not produced in sufficient quantities Certain microorganisms of the human microbiota are however able to synthesise vitamins which can then be utilised by the host.
Gastrointestinal microbiota such as Escherichia coli and Bacteroides fragilis synthesise vitamins including B1, B2, B5, B6, B12, folic acid and biotin. Perhaps the most well-known example is cobalamin vitamin B12 , a vitamin which acts as a coenzyme in DNA metabolism and is crucial to erythrocyte maturation.
Enzymes needed for B12 synthesis found in neither plants nor animals, but rather in the bacteria living within the human body. Furthermore, it is thought that half of the daily Vitamin K requirement is supplied by gut bacteria.
The mucosal immune system is so specialised, in fact, that its functions are, for the most part, independent of the systemic immune system. Toll-like receptors TLRs are found on the membranes of non-immune cells and leukocytes; they are involved in this recognition and suppress inflammatory responses, stimulating immunological tolerance to the microbiota.
The gastrointestinal microbiota has been proved to modulate neutrophil function and migration and also to stimulate the differentiation of T lymphocytes into various helper T cells Th — including Th1, Th2 and Th17 — or into regulatory T cells Tregs.
Th17 cells secrete several pro-inflammatory cytokines, playing a critical role in host defence by attracting neutrophils and macrophages to infected tissues. Interestingly, the SCFA butyrate has been shown to induce the differentiation of Tregs and analysis has suggested that the luminal concentrations of SCFAs is positively correlated with the number of Tregs in the colon.
Tregs are vital in controlling the immune response and the prevention of autoimmune diseases; people with Type 1 Diabetes Mellitus have a deficit of butyrate-producing bacteria in the gut providing some evidence for this butyrate-autoimmunity connection. Furthermore, the host-commensal communication stimulates antimicrobial responses to foreign pathogens from the epithelium. This involves the release of antibacterial lectins — including alpha defensins and angiogenins — that help to decrease the number of pathogenic microbes in the body and thus prevent abnormal immune responses.
For example, Bacteroides thetaiotaomicron a bacterium commonly found in the human gastrointestinal tract stimulates the production of antimicrobial peptides which in turn target pathogenic microorganisms. Commensal viruses could potentially also protect the host from pathogenic infections from other viruses. Several studies have shown that HIV patients containing this commensal virus tend to live longer than HIV-infected subjects without the virus The mechanism behind this is unknown, however it is thought that it involves blocking interactions between cell surface receptors found on helper T cells that are necessary for HIV virus replication.
Interestingly, one of the key ways in which the microbes in the gut protect the human body is by occupying spaces that could otherwise be colonised by harmful pathogens. This mechanism of colonisation resistance is not a new idea.
Indeed, 50 years ago, work from Bohnhoff et al. Though the phenomenon of colonisation resistance may seem simple, the mechanisms of microbiota-mediated colonisation are incredibly complex. Competition for nutrients in the gut is fierce and exogenous microorganisms are therefore unlikely to find an uncontested niche; they must compete with the established microorganisms for nutrients.
Citrobacter rodentium C. Such studies have found that commensals are often able to outcompete C. Therefore, pathogen colonisation is largely controlled by competition with metabolically similar commensal microorganisms. The gut-brain axis is by definition a bidirectional link between the central nervous system CNS and the enteric nervous system ENS. Several studies have suggested that there is a link between gut microbial composition and certain diagnoses; it is important to remember that though these studies may show strong correlations, there is not yet enough evidence to suggest causal relationships.
Furthermore, it must be considered that much of the research into this topic involves studies on germ-free GF mice and it can be unreliable to extrapolate results to humans. However, work with GF mice has indicated the evolutionary importance of the microbiome and consequent effects in mammalian behaviour. Evidence from human studies has further made it clear that there is a correlation between cognitive function and the microbiome of the gut.
The absence of microbial colonisation is associated with an altered expression and turnover of neurotransmitters in both the CNS and the ENS. Microbes keep us slim. Microbes play an important role in our body shape by helping us digest and ferment foods, as well as by producing chemicals that shape our metabolic rates. Microbes detoxify and may even fight off stress. Just as humans breath in oxygen and release carbon dioxide, microbes in and on us take in toxins and spare us their dangerous effects.
A recent study also shows that people feeling intense stress have much less diverse bacterial communities in the gut, suggesting that there is a not-yet-understood interplay between microbes and stress responses.
Microbes keep babies healthy. Recent studies have shown that babies born via caesarean section have very different microbiomes than those born the old-fashioned way.
Because during the birthing process, babies are colonized with the microbes of their mother, especially substances that aid in the digestion of milk. According to Science News , babies born via C-section are more likely to develop allergies and asthma than children born vaginally.
And yet, much more research needs to be done to determine what different microbes do, and whether their disturbance causes ailments or is simply correlated to various health issues. To read more, head to Dr. Pingback: What is Rewilding? Pingback: develop an idea for a health education plan centering on the beneficial nature of microbes.
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