Biol 243 Medical Microbiology Biology Essay


Every living organism is made up of cells and every organism is made up of either two types of cells which are either Prokaryotic or Eukaryotic cells. Bacteria are a group of prokaryotic organisms and are a diverse group of organisms which belong to the domain Archea. Bacteria can act as pathogens which can cause systemic infections and Bacteria can be subcategorised into gram-positive bacteria and gram-negative bacteria where gram-positive bacteria such as Streptococcus pneumoniae have a large layer of peptidoglycan and can be treated with antibiotics such as penicillin and gram-negative bacteria have a smaller layer of peptidoglycan as well as lipopolysaccharide and as a result, gram-negative bacteria such as Vibrio cholera cannot be treated with antibiotics that work with gram-positive bacteria.

Bacteria do also live within humans (2) and exist as integral part of humans because after birth, bacteria and other microbes exist as a Biofilm within the human body which means they are ubiquitous in the human body and are known as the 'Microbial fauna'. So from this information we can gather that bacteria do cause harm because they can cause systemic infections however they are also an integral part of humans so the essay is now going to compare whether bacteria cause more harm than good.

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Bacteria do cause harm and can cause severe infections especially gram-negative bacteria such as Vibrio cholera because the systemic infections which are particularly harmful, including symptoms of diarrhoea and potentially death and this shows that bacteria can cause harm.

Bacteria can cause harm by producing virulence factors which can be either offensive, defensive or non-specific where offensive virulence factors are toxins which can be subdivided into endotoxins and exotoxins. Exotoxins are produced by both gram-negative and gram-positive bacteria whereas Endotoxins are produced only by gram-negative bacteria. Endotoxins are Lipopolysaccharide which are a integral part of the bacterial cell wall and these toxins are weaker than exotoxins e.g. LD50 of Botulinum toxin is 25pg whereas the LD50 for endotoxins range from 200-400µg.

Different bacterial infections have different prevalence's in different countries across the world. In 2010 (3) 179,379 people were identified with cholera in Haiti whereas developed countries like Canada had only 2 people identified with cholera (World Health Organisation, 2012). This shows that bacterial infections can affect a wide range of people and that bacteria are disadvantageous to humans as the infections caused can affect several of the hosts systems and can cause debilitating diseases such as Cholera or Botulism so bacteria are not beneficial for humans.

However bacteria are also beneficial for humans (4) because there are 1014 bacterial organisms including approximately 800 bacterial species found in the vicinity of the oral cavity and that live within humans and these are part of the normal human flora. A large number of bacteria contribute to the human flora and help provide a way to enhance digestion, absorption as well as prevention of disease. The normal human flora is an essential barrier to potential pathogens e.g.Staphylococcus aureus and the normal human flora prevents pathogens from attaching to the Biofilm so pathogenic bacteria cannot release virulence factors causing disease and as a result bacteria help prevent disease which shows that bacteria are essential for humans to survive from infectious diseases which may come from bacteria.

In the large intestine microbial fauna, bacteria provide a source of vitamin K and vitamin B12 and these are important molecules for the body as vitamin k is required to creates factors II,VII,IX and X for the coagulation cascade and deficiency in vitamin K will lead to abnormal bleeding and Vitamin B12 is required for DNA synthesis as it is used to synthesise nitrogenous bases such Guanine so lack of vitamin B12 can lead to diseases such as Megaloblastic Anaemia. Hence Bacteria are advantageous for humans as they provide Vitamin K and B12 and this helps prevents diseases such as Megaloblastic Anaemia which shows that Bacteria are beneficial for humans.

However substantial damage to natural barriers such as the skin allows normal safe bacteria found in the microbial fauna to become opportunistic pathogenic and these opportunistic pathogens can cause severe infections. One example of a normal bacteria which is a component of the microbial fauna and is then opportunistic are bacteria belonging to the Genus, Staphylococcus and in particular Staphylococcus aureus and this can cause a variety of infections including skin infections, Pneumonia, food poisoning and many more and as a result, Staphylococcus aureus is a major pathogen found in many nosocomial infections ( Malachowa & Deleo, 2010).

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There are several gram-negative bacteria which are major causes of hospital-acquired infections (5) and these organisms include E.coli, P.aeruginosa and E.cloacae and these pathogenic bacteria can affect multiple systems and organs including blood, skin and Gastrointestinal Tract (Po-ren Hseuh et al ., 2005).

In hospitals nosocomial infections caused by bacteria can be treated with antibiotics (6) which are drugs which kill the bacteria by several different mechanisms e.g. penicillin prevents the bacteria from synthesizing the cell wall and different antibiotics are used for different bacterial pathogens, so by using antibiotics we can prevent bacterial infections and this shows that even though bacteria can cause disease, humans have drugs which can deal with these diseases, so bacteria do not cause as much harm to humans.

However there are many bacterial organisms such as Staphylococcus aureus which develop resistance to very powerful antibiotics such as Vancomycin so due to excess antibiotic use, bacteria are now becoming resistant to drugs, so they are causing more severe systemic infections which can affect many of the host systems and can cause life-threatening illnesses so bacteria do cause harm to humans .

Another reason why Bacteria are beneficial for humans is that bacteria have to use fermentation (7) which is a mechanism which oxidises NADH to NAD+ and creates a fermentation waste product which can be a useful commercial product for humans. In fermentation electrons are transferred from an electron carrier such as NADH and this is passed down to another metabolic molecule which then creates a fermentation waste product such as ethanol or Lactic acid.

Fermentation waste products such as Lactic acid (8) can be produced by bacterial organisms such as the Bacterium Bacillus coagulans (Maas et al., 2008) and Lactic acid can be used to produce commercial products such as Cheddar cheese, yoghurt and soy sauce.

Bacteria belonging to the species 'Clostridium' are bacteria which utilise fermentation as a mechanism to sustain metabolism and create useful fermentation products such as nail polish remover or rubbing alcohol which shows that Clostridium bacteria are beneficial to humans however Clostridium species are gram-positive bacteria which are found in the environment and these are often responsible for spoiling canned food and can produce endotoxins which can cause systemic disease and infection. In particular Clostridium botulinum is a pathogen which secretes the Botulin toxin and causes the disease Botulism.

Another benefit of bacteria is medical applications of photosynthetic bacteria (9) because photosynthetic bacteria can allow synthesis of metabolic substances including Ubiquinone which is an electron carrier used in the Respiratory chain, Vitamin B12 which is deficient in Megaloblastic anaemia as well as Streptokinase which is a thrombolytic agent used to dissolve blood clots and can treat Myocardial infarctions. Another Photosynthetic bacteria, 5-aminoleukivic acid is used as a cancer treatment and is also used to treat less chronic conditions such as Acne Vulgaris (Sasaki et al., 2005).

Also experimental trials (S.Guandalini et al.,2000) showed that the probiotic Lactobacillus can be used as a medical treatment (10), because it was given to children with acute diarrhoea and the results showed that Lactobacillus reduced the effects of the acute diarrhoea and could also possibly prevent an infection from occurring again in the future, so this shows that Bacteria do have many advantages for humans.

Overall I believe that bacteria do not cause more harm than good because this essay shows that bacteria are an essential part of the human flora and prevent microbial infections from pathogens such as bacteria, viruses and fungi. They also produce useful commercial products used in everyday life such as cheese and nail varnish remover however when the body is immunocompromised, bacteria can cause severe systemic infections and cause deadly diseases and although we can treat bacterial infections with antibiotics, more and more bacteria are becoming antibiotic resistant so bacteria whilst useful can cause problems. Nevertheless bacteria can also be used in a therapeutic manner e.g. streptokinase is used to dissolve blood clots and bacteria also provide essential vitamins such as Vitamin K and this shows that bacteria can be used in a helpful manner for humans and although bacteria cause life-threatening diseases, without bacteria, humans would not be able to survive hence bacteria do not cause more harm than good.

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