Microbiology: Definition, Role of Microbes in Sewage Treatment, Compost Breakdown, Food Industry, Health and Drug Industry

This article discusses the definition of microbiology and the role of microbes in sewage treatment, compost breakdown, food industry, health, and drug industry. It also includes information on Candida albicans, Staphylococcus epidermidis, Lactobacillus acidophilus, Streptococcus thermophiles, Poliovirus, and Streptococcus mutans.

Running head: MICROBIOLOGY
MICROBIOLOGY
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MICROBIOLOGY
Question 1: Definition of microbiology
The specific study regarding the microorganisms that are invisible with naked eyes
including both the unicellular and cluster of cell is termed as microbiology. Microbiology
includes the in-depth study of eukaryotes like Protista and fungi and prokaryotes like algae and
bacteria. The study includes viruses as well. Study of different organism is termed differently,
for example, virology for viruses, bacteriology for bacteria, mycology for fungi and parasitology
for parasites and others (Murray, Rosenthal &Pfaller, 2015).
Question 2
Role of the microbes in sewage treatment
Sewage is a type of a mixture that contains waste eater, and domestic wastes from the
toilets. The sewage is composed of both organic and the dissolved inorganic matters. After the
removal of the solid materials by filtration, the effluent that remains is rich in pathogenic
microbes and suspended organic substances (Grady et al., 2011). The effluent is fed in the
aeration tanks containing some complex community of microbes. The microbes uses the organic
material in the sewage as a source of carbohydrate for the respiration.
Two type of microbial processes occur in the sewage treatment. After the completion of
the primary treatment, the liquid and the solid phases of the sewage are separated physically. The
two crucial steps in this process is nitrification and removal of phosphorus. The ammonia is
converted to nitrate by Nitrosomonas. The nitrate is further oxidised to nitrite by Nitrobacterspp.
This is the aerobic process that occurs in the sewage treatment (Grady et al., 2011).

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In the liquid effluent, the denitrifying bacteria reduces the nitrate to dinitrogen gas that
liberates the nitrate from the sewage. The key microorganisms used in the process are members
of Nitrosomonas, who are responsible for the initial step of nitrification; that is the oxidation of
nitrite to nitrate and Psedomonas in the anaerobic process, helping to reduce the nitrate in to
dinitrogen gas.
Figure: a simplified diagram of a sewage treatment process

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Source:- (Grady et al., 2011).
Role of the microbes in compost breakdown
Microorganisms play an important role in the recycling of the wastes from agriculture. At
the time of composting the mesophilic bacteria utilises the simple nutrients raising the
temperature of the soil. The proliferation of the thermophilic microbes takes place in the second
phase. In the thermophilic stage the heat tolerant organisms are destroyed. The high temperature
helps in the degradation of the proteins and the complex polymers. Lignocellulose that is the
essential component of the plant vascular biomass. In the curing phase the Mesophilic bacteria
plays the key role (Singh & Nain, 2014). Decomposition of the fermented products, production
of methane and other noxious gases takes place. Fungi like Trichoderma and Phanerochaete can
degrade lignocellulose. Cellulomonas and Cytophaga are the aerobic mesophilic bacteria that
has got the ability to degrade cellulose (Singh & Nain, 2014).
Question 3
Role of microbes in the food industry
Microorganisms, especially bacteria and fungi play an important role in the food industry.
A variety of important food in our diet is produced with the help of microorganisms. Example,
Lactobacilli, is a type of facultative anaerobic bacteria that plays an important role in the
preparation of dairy products, fermented vegetables, sourdough bread and more (Ray & Bhunia,
2013).
Examples:-
A fermented product called cultured butter milk is produced with the help of a mixture of
Streptococcus lactis or S, cremoris with the aroma producing Leuconostoc dextranicum. S.

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Lactis converts the lactose sugar of milk to form lactic acid that causes the milk to curdle
(Prescott & Dunn, 1949). Again the function of Leuconostoc is the production of a type of
volatile substance that imparts a typical odour to cultured butter milk (Doyle & Buchanan,.
2012).
Again yeasts are able to ferment sugar to ethanol and carbon dioxide, due to which they
are extensively used in food industry. Baker’s yeast; Saccharomyces cerevisiae is largely used in
baking. Yeast serves three prime functions. It produces carbon dioxide by breaking down
fermentable sugar present in the dough (Prescott & Dunn, 1949). The expansion of the dough is
facilitated by the evolution of the carbon dioxide. It also causes the maturation of the dough by
producing alcohol and acids on flour proteins. This gives the light airy structure. At the time of
the fermentation of the dough yeast produces a many secondary metabolites like ketones, higher
alcohols, aldehydes, esters, organic acids. They react to form complex flavour compounds,
giving characteristic flavour to the bread (Ray & Bhunia, 2013).
.
Glucose Yeast enzyme Ethyl alcohol + Carbon dioxide
Question 4
Role of microorganisms in health
Many microorganisms residing in our body plays a fundamental role in human health.
These normal microbial floras are present in different parts of the body including skin, gut, oral
cavity and vagina. Most of the human microbiome stays in mutualistic relationship with the host.
They compete with the pathogenic microbes for colonisation and nutrition and thus help to keep

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them away from the body. They play an important role in our immune system (Murray,
Rosenthal & Pfaller, 2015).
Example: - Escherichia coli is the normal flora present in the gut that helps in the
production of useful substances like vitamin B12 and Vitamin K. The normal flora of the
intestine also produces enzymes like galactosidase, glucosidase and cellulose that aids in food
digestion.
Role of the microorganisms in drug industry
The commercial production of penicillin and antibiotics is one of the dramatic case
histories in the field of industrial microbiology. Microorganisms are being used in
pharmaceutical industry for achieving special modifications of complex drug molecules like
steroids. Microorganisms are widely used in the production of vaccines. There are other variety
of medicinal agents’ obtained from the microorganisms like vitamins, amino acids, iron chelating
agents, dextrans and certain enzymes (Wood, 2012).
Example:- antibiotics are the known group of secondary metabolite produced by certain bacteria
and fungi, that can be harmful for the other microorganisms. These secondary metabolite
production in the life cycle of microbes in restricted for certain groups of microbes (Prescott, &
Dunn, 1949). These secondary metabolites do not help in the growth of the organisms but
usually have other functions. Industrially antibiotics are produced by batch fermentation process.
Ex- Penicillin produced by Penicillium notatum, Cephalosporin produced by a marine fungus
Cephalosporium acremonium.
Question 5:
Candida albicans:

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Opportunistic pathogens are referred to such pathogens that utilise several opportunities
such as weak immune system in order to cause illness. They can remain in the body as dormant
and do not cause any disease symptoms, however, in favourable condition they could multiply to
overwhelm situation and weakened the defences of body (Seng et al., 2013). Candida albicans
remains as the common flora of human gut but in case of weak immune system it could become
pathogenic and lead to the consequence of candidiasis in oral cavity, GI tract, urinary tract and
others for over growth of the organism (Markey et al., 2013). Due to such characteristics
Candida albicans can be considered as opportunistic pathogen.
Staphylococcus epidermidis:
The bacteria that are remained in the human body as semipermanent basis and do not
cause any disease are called normal flora (Murray, Rosenthal &Pfaller, 2015). The gram positive
bacteria Staphylococcus epidermidis remains in the human skin and sometimes in the mucosa as
normal flora and usually does not cause any pathogenic consequence. However, in case of weak
immune system it may cause infection, especially hospital acquired infection for the patient that
use catheters (Markey et al., 2013). Thus, it can be said that the organism may be act like
opportunistic pathogen in favourable condition.
Lactobacillus acidophilus:
Lactobacillus acidiphulus resides in the human gastrointestinal tract and does not
associated with any disease causing condition. In addition the gram positive bacteria helps in
different fermentation and sometimes act as probiotic as well (Seng et al., 2013). Thus, it can be
said that Lactobacillus acidophilus is a normal flora.
Streptococcus thermophiles:

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There are some microorganisms that do not cause any harm to the host, rather they are
beneficial for the host. In such cases the host body provides them effective environment to grow
and the organisms provide adequate advantages to the host body. Such organisms are known as
mutualists (Murray, Rosenthal &Pfaller, 2015). The bacteria Streptococcus thermophiles is
identified as the human gut flora, however, they do not cause any harm to the host instead they
help to reduce antibiotic associated diarrhoea (Seng et al., 2013). Thus, it can be said that
Streptococcus thermophiles is included in the group of mutualists.
Poliovirus:
Pathogens are defined as the microorganisms that are responsible for the disruption of the normal
physiology of animals and plants as well. In this regards viruses play an important role in order
to cause infection and interfere with the normal function of the body (Markey et al., 2013).
Poliovirus is one of the most infectious viruses and act as the responsible agent of poliomyelitis.
The disease mainly affects the muscle strength of the patient and results in inability to move
(Murray, Rosenthal &Pfaller, 2015). Thus, Poliovirus can be considered as a potential pathogen.
Streptococcus mutans:
Like pathogens that causes infections or other disease causing conditions, the gram
positive bacteria Streptococcus mutans that are found in the oral cavity of humans also
contributes to specific pathogenic condition such as dental decay (Seng et al., 2013). Thus, the
bacteria Streptococcus mutans can be considered as pathogen.

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References
Doyle, M. P., & Buchanan, R. L. (Eds.). (2012). Food microbiology: fundamentals and frontiers.
American Society for Microbiology Press.
Grady Jr, C. L., Daigger, G. T., Love, N. G., & Filipe, C. D. (2011). Biological wastewater
treatment. CRC press.
Markey, B., Leonard, F., Archambault, M., Cullinane, A., & Maguire, D. (2013). Clinical
Veterinary Microbiology E-Book. Elsevier Health Sciences.
Murray, P. R., Rosenthal, K. S., & Pfaller, M. A. (2015). Medical microbiology. Elsevier Health
Sciences.
Prescott, S. C., & Dunn, C. G. (1949). Industrial microbiology. Industrial microbiology.
Ray, B., & Bhunia, A. (2013). Fundamental food microbiology. CRC press.
Seng, P., Abat, C., Rolain, J. M., Colson, P., Lagier, J. C., Gouriet, F., ...&Raoult, D. (2013).
Identification of rare pathogenic bacteria in a clinical microbiology laboratory: impact of
MALDI-TOF mass spectrometry. Journal of clinical microbiology, JCM-00492.
Singh, S., & Nain, L. (2014, June). Microorganisms in the conversion of agricultural wastes to
compost. In Proc Indian NatnSciAcad (Vol. 80, No. 2, pp. 473-481).
Wood, B. J. (2012). Microbiology of fermented foods. Springer Science & Business Media.