The human body is inundated with plethora of harmless microorganism’s including fungi and bacteria found in different parts of the body (Figure 1). These organisms which are generally known as normal microflora are found in both the external and internal part of the body. The relationship between indigenous microorganisms of humans (i.e. normal microflora) and the human body or host itself is a typical example of a host-parasite relationship or host-microbe association that is usually beneficial to both the host and the microbe in the relationship.
There is usually a state of equilibrium maintained between the host and the microbe; and this balance ensures that the host and the normal microflora coexist together and survive mutually without causing harm or injury to each other. This state of balance between the host and the normal microflora is normally experienced when the human host in particular is in a healthy state. A functional immune system aside other physiological or physical barrier of the body such as an intact skin helps the host to maintain a state of equilibrium that allow both the normal microflora and the host to coexist without the development of an infectious disease.
Disease or infection usually develops when this state of balance or equilibrium in the body is disrupted either by disease development or dilapidated immune system. The development of disease or infection in this case could be caused by endogenous microorganisms – which are microbes innately found in the host such as normal microflora or from exogenous microorganisms – that emanate from the environment or from other infected humans, animals or fomites.
Normal microflora which can also be referred to as flora or normal microbiota is the totality of microorganisms that are inherently present in a particular environment, body or location at every specific point of time. They generally refer to harmless microorganisms that are frequently found in particular anatomical sites of a healthy host including humans and animals. And it is worthy of note that the terms normal microflora, microflora, indigenous flora, normal commensal flora and normal microbiota are used synonymously to mean the same thing.
Resident microflora (autochthonous flora) are those microorganisms which are permanent dwellers or natural inhabitants of a particular environment or body at any given point of time while transient microflora (allochthonous flora) are microorganisms which only have a temporary habitation in an environment or body at any given time. Microorganisms become transient when they move from one part of the body or their natural environment to another. The microorganisms that naturally make up the microbiota of the human body are normally harmless and they pose no potent danger to the health of the individual. These harmless microorganisms play a variety of important role in the entire upkeep and protection of the human body from disease-causing microorganisms (pathogens), and many floras in the digestive system of humans also aid digestion and other internal metabolic activities by secreting substances or enzymes that spur or fasten these processes.
Microbiota which can also be called normal microflora is the totality of microorganisms that are inherently present in a particular environment, body or location at every specific point of time. Mycoflora are fungal organisms that live in particular sites of the body without causing infection or disease. Microbiota goes into competition with pathogens on and in the human body with a view to subverting their pathogenic and virulent activities within the host. They do this through a process called amensalism (a bacterial interference mechanism). In amensalism, normal microflora utilize available space, nutrients and other resources in the host (required by the pathogen to cause infection and disease) and produce substances that resist their disease-causing mechanisms in the host.
Normal flora can also become opportunistic microorganisms which only cause disease in the host by chance i.e. when the environment or body of the individual favors their blossoming (e.g. in an immunocompromised case such as in an AIDS patients or an individual whose immune system has been suppressed due to therapy). The overuse of antibiotics, stress and nutritional imbalance in human beings can cause their microbiota to become pathogenic in nature. The microbiologist should acquaint him or herself on the basic knowledge of the different microbiota that make up different parts of the human body or the environment from which the samples they will be working with in the laboratory are actually made up of. This will allow the scientist to make concrete conclusions on the inferences drawn from a particular research or test so that the final judgment of an experiment is not based on the microbiota (which are not harmful and might not necessarily be the target or cause of the malady being deciphered).
Figure 1: Human anatomy showing sites of the body colonized by microorganisms.
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