Current Concept Of Microbiology And Diseases Biology Essay

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There are more microorganisms in our body than there are people on the planet, this statement shows how important these microbes are in our life. The relationship of microorganisms with our life is the basic theme of this article. These microorganisms (bacteria, viruses, fungi and algae) are minute things with smaller size and therefore cannot be seen with the naked eye. Few decades before, thousands of people were died with unknown causes, but later known as pathogenic microorganisms.

From this article we can get an idea of current concept of microbiology (Study of microorganisms).

Staphylococcus is a genus which contains up to 32 species. (Harris and Foster, 2002). These Gram-positive, spherical bacteria occur in the form of bunch of grapes. Staphylococcus can survive in the presence and in the absence of oxygen. These bacteria produce many toxins that contribute to its pathogenicity, these toxins are common cause of food poisoning. Staphylococcus is not very highly virulent (Degree of potency). It resides on the skin and mucous membrane of humans. It causes eye inflammation and superficial skin infection.

Streptococcus pyogenes and Streptococcus pneumonia

Streptococcus pyogenes

S. pyogenes is Gram-positive, round bacterium which can grow in the form of long chains. S. Pyogenes are the most common bacteria of human. It has capsule around itself which increases its virulence. S. pyogenes mostly begins infection on skin or in the throat, from there; it starts to spread deeper into skin, which can lead to various diseases like scarlet fever, pharyngitis and toxic shock syndrome.

Streptococcus pneumonia

These are Gram-positive bacteria, oval cocci and typically present in the form of pairs. These bacteria can live without oxygen. The most common feature of S. pneumonia is they have capsule. These bacteria are most common cause of pneumonia. This disease is spread through direct contact with people who carry the bacteria in their throat. 

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a rod shaped, G-negative bacterium, which can cause diseases in animals and humans. It has specific grape like odor. It is found in water, soil and skin. Exposure to aerosol of contaminated water is risk factor for P. aeruginosa. It produces a toxin called pyocyanin which is its virulent factor. (Raymond S et al., 1994). It can cause infection in lower respiratory tract, urinary track wound and blood infection.

Mycobacterium tuberculosis

Mycobacterium tuberculosis is Gram resistant, rod shaped and aerobic bacterium. Its cell wall is enriched in lipid which makes it resistant to our immune system. In 2008 there were an estimated 8.9-9.9 millions incident cases of M. tuberculosis (World Health Organization, 2008). It spreads through air and resides in mammalian respiratory system and infects the lungs.

Enterococcus spp.

These are the part of normal intestinal flora. These are Gram-positive cocci. They do not need oxygen for their metabolism. Enterococcus is not very highly virulent and cause disease in patients who are already under stress of other bacteria. This bacteria causes 10-15% of urinary tract, intra abdominal and blood stream infections. (Ryan and Ray, 2004).

Clostridium spp.

It is rod shaped and Gram-positive genus of bacteria which consist of at least 100 species. It can form spore (thick coating) around itself and prevent its genetic material in unsafe environment so can live for a long time. Clostridium lives in all anaerobic environments like soil, aquatic sediments and intestinal tracks of animals.

Different species are the causative agents of different diseases like C. tetani causes tetanus, C. perfringens causes gas gangrene.

Bacillus cereus

Bacillus cereus is the responsible of food born diseases in most cases. It is rod shaped and Gram-positive bacterium. It is present everywhere in soil, air, poorly handed food and in our gut. It can survive in an aerobic and anaerobic environment. Bacillus cereus produces different toxins like emetic and enterotoxaemia. Its infection is characterized by nausea, vomiting and severe diarrhea.

Vibrio cholera

Vibrio cholera is comma shaped, Gram-negative bacterium having a flagellum on one of its end which help it to move. V.cholera affects millions of people and causes thousands of deaths in endemic area. The organisms transferred by the ingestion of contaminated water and food, and reside in the wall of small intestine and produce enterotoxaemia there. It cause watery diarrhea and death of patient occur due to dehydration. In 1994 cholera cases were notified from 94 countries in one year. (WHO, 1995).


Salmonella is a rod-shaped, Gram-negative and non-spore forming bacterium, having flagellum, which projects from all directions. Salmonella is a major cause of food borne illness. The organisms transfer through the contaminated food of animal origin, like raw material, poultry, eggs and milk. Salmonella can also a causative agent of typhoid fever caused by Salmonella typhi. In USA 40,000 cases of salmonella infection appear each year (US centers for disease control and prevention, 2000). General signs and symptoms of Salmonella infection are nausea, vomiting, abdominal pain, fever and diarrhea.

Escheridia coli

E. coli are a rod-shaped and Gram-negative bacteria. Fimbriae are present on its surface through which they can attach to human epithelial cells. Human intestinal flora is the major reservoir of these bacteria. E,coli are classified according to virulence properties.

Enterotoxigenic E.coli (ETEC)

Enterotoxigenic E.coli is the major causes of traveler's diarrhea in developing countries (Northey G et al., 2007).Transmission of bacteria occur by consumption of food and water. ETCE diarrhea is caused by toxin (enterotoxines) in intestines. Its causes watery diarrhea and abdominal cramping and fever.

Enterohaemorrhagic E. coli (ETEC)

Escherichia coli (ETEC) is a bacterium that is commonly found in the gut of humans and warm-blooded animals (WHO, 2005). It is common cause of bloody diarrhea. EHEC E.coli transferred from the food from animal source like meat and unpasteurized milk.

Neisseria gonorrhoeae

N.gonorrhoeae is a Gram-negative, kidney shaped bacterium, which is a causative agent of sexually transmitted disease gonorrhea. People under twenty five years who have multiple sex partners are mostly infected with gonorrhoeae (US centers for disease control and prevention 2000). In men the infection is present in urethra and in women in the uterine cervix. Asymptomatic male and female are the real reservoir of N.gonorrhoeae.

Chlamydia trachomatis

C. trachomatis is round a bacterium which is the causative agent of most common sexually transmitted disease, Chlamydia double then the gonorrhoeae. There were more than 1.2 million cases of Chlamydia reported in USA in 2008(CDC). The reservoir of this bacterium is urethra, rectum, conjunctiva and uterus.


Microorganisms are present all around humans. Out of these some are beneficial and some are pathogenic. Microbiological science is helping mankind in both the aspects by providing ample knowledge about the pathogens and non pathogens. Moreover, recent studies on pathogens helped health related departments in curing the human miseries.