Monday, 16 September 2013

Bacteria:An organism of great diversity

Introduction to the Bacteria

Bacteria are often maligned as the causes of human and animal disease (like this one, Leptospira, which causes serious disease in livestock). However, certain bacteria, the actinomycetes, produce antibiotics such as streptomycin and nocardicin; others live symbiotically in the guts of animals (including humans) or elsewhere in their bodies, or on the roots of certain plants, converting nitrogen into a usable form. Bacteria put the tang in yogurt and the sour in sourdough bread; bacteria help to break down dead organic matter; bacteria make up the base of the food web in many environments. Bacteria are of such immense importance because of their extreme flexibility, capacity for rapid growth and reproduction, and great age - the oldest fossils known, nearly 3.5 billion years old, are fossils of bacteria-like organisms.

Bacteria grow in a wide variety of habitats and conditions.

Bacteria are so widespread that it is possible only to make the most general statements about their life history and ecology. They may be found on the tops of mountains, the bottom of the deepest oceans, in the guts of animals, and even in the frozen rocks and ice of Antarctica. One feature that has enabled them to spread so far, and last so long is their ability to go dormant for an extended period.
When most people think of bacteria, they think of disease-causing organisms, like the Streptococcus bacteria growing in culture in this picture, which were isolated from a man with strep throat. While pathogenic bacteria are notorious for such diseases as cholera, tuberculosis, and gonorrhea, such disease-causing species are a comparatively tiny fraction of the bacteria as a whole.

Bacteria have a wide range of envronmental and nutritive requirements.

Most bacteria may be placed into one of three groups based on their response to gaseous oxygen. Aerobic bacteria thrive in the presence of oxygen and require it for their continued growth and existence. Other bacteria are anaerobic, and cannot tolerate gaseous oxygen, such as those bacteria which live in deep underwater sediments, or those which cause bacterial food poisoning. The third group are thefacultative anaerobes, which prefer growing in the presence of oxygen, but can continue to grow without it.
The other group, the autotrophs, fix carbon dioxide to make their own food source; this may be fueled by light energy (photoautotrophic), or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic). While chemoautotrophs are uncommon, photoautotrophs are common and quite diverse. They include the cyanobacteria, green sulfur bacteria, purple sulfur bacteria, and purple nonsulfur bacteria. The sulfur bacteria are particularly interesting, since they use hydrogen sulfide as hydrogen donor, instead of water like most other photosynthetic organisms, including cyanobacteria.

Bacteria play important roles in the global ecosystem.

The ecosystem, both on land and in the water, depends heavily upon the activity of bacteria. The cycling of nutrients such as carbon, nitrogen, and sulfur is completed by their ceaseless labor.
The cycling of nitrogen is another important activity of bacteria. Plants rely on nitrogen from the soil for their health and growth, and cannot acquire it from the gaseous nitrogen in the atmosphere. The primary way in which nitrogen becomes available to them is through nitrogen fixation by bacteria such as Rhizobium, and by cyanobacteria such as AnabaenaNostoc, and Spirulina, shown at right. These bacteria convert gaseous nitrogen into nitrates or nitrites as part of their metabolism, and the resulting products are released into the environment. Some plants, such as liverworts, cycads, and legumes have taken special advantage of this process by modifying their structure to house the basteria in their own tissues. Other denitrifying bacteria metabolize in the reverse direction, turning nitrates into nitrogen gas or nitrous oxide. When colonies of these bacteria occur on croplands, they may deplete the soil nutrients, and make it difficult for crops to grow.


Bacteria consist of only a single cell, but don't let their small size and seeming simplicity fool you. They're an amazingly complex and fascinating group of creatures. Bacteria have been found that can live in temperatures above the boiling point and in cold that would freeze your blood. They "eat" everything from sugar and starch to sunlight, sulfur and iron. There's even a species of bacteria—Deinococcus radiodurans—that can withstand blasts of radiation 1,000 times greater than would kill a human being.
But infectious bacteria can make you ill. They reproduce quickly in your body. Many give off chemicals called toxins, which can damage tissue and make you sick. Examples of bacteria that cause infections include StreptococcusStaphylococcus, and E. coli.
Antibiotics are the usual treatment. When you take antibiotics, follow the directions carefully. Each time you take antibiotics, you increase the chances that bacteria in your body will learn to resist them. Later, you could get or spread an infection that those antibiotics cannot cure.

Types of Bacteria.

Bacteria fall into a category of life called the Prokaryotes (pro-carry-oats). Prokaryotes' genetic material, or DNA, is not enclosed in a cellular compartment called the nucleus.
Bacteria and archaea are the only prokaryotes. All other life forms are Eukaryotes (you-carry-oats), creatures whose cells have nuclei.

5 Types of Harmful Bacteria

Streptococcus Pyogenes is the causative agent of mild sore throat and skin infections that may worsen in certain situations to lead to life threatening infections like toxic shock syndrome and septicemia (when bacteria gain access to the blood stream). It is classified as gram positive coccus that grows mainly in chains.
E- Coli is a gram negative bacillis as discussed previously and is considered as a causative agent of traveler’s diarrhea; however some pathogenic strains can also lead to bloody diarrhea and circulatory shock.

Vibrio cholerae is the causative agent of cholera and is associated with intake of improperly cooked food or poor sanitary conditions. Vibrio Cholerae is linked to hundreds and thousands of deaths worldwide (mostly in under- developed countries) due to cholera outbreak.

The most common causative agent of food poisoning throughout the world is Enteritis salmonella and can lead to serious and life threatening food poisoning, diarrhea, circulatory shock and dehydration in children. Infection can be controlled by timely intake of proper antibiotics and circulatory support.

Salmonella Typhi is a gram negative organism that is the causative agent of typhoid fever. It is associated with a high mortality rate after initial infection and characterized by blood diarrhea, vomiting, dehydration, fever and may lead to death if proper treatment is not instituted at the right time.

5 Types of Beneficial Bacteria

Lactobacillus acidophilus exists in different parts of human body like intestine, vagina and oral cavity. It is responsible for slightly acidic pH of vagina that is helpful in preventing overgrowth of other microorganisms. In addition it is also known to boost immunity.
Bacillus subtilis occurs independently in the environment around us and was first used by Nazi army to manage diarrheal illness. It helps in normalizing gut motility and metabolic functioning.
Bifidobacterium animalis is found in the intestine of animals and humans as a normal commensal that aid in digestive process. In addition it can also be consumed in supplemental doses to improve the symptoms of constipation or irritable bowel syndrome.
Streptococcus thermophilus is classified under coccus and it has the ability to withstand a temperature of about 212 degrees Fahrenheit. Streptococcus thermophilus strengthen immunity and improves the functioning of gut. It can be obtained from cheese and other dairy products.
Lactobacillus reuteri is one of the probiotics agents that are present in maternal breast milk and becomes a permanent part of gut flora. It is also present in dietary sources like yogurt and cheese.

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