Sunday, 14 April 2013

The Smallest – The Largest

Hi friends. I am here again. Let me share something exciting with you. Yesterday morning I got my dream microscope in my hands. Wow! The feeling was just wow I mean. After getting into the university, from the first year onward, I was dreaming of having this microscope on my own and making a little, a very little  laboratory inside my room. So, friends I think the first step towards creating  this little laboratory is fulfilled. Ahh, thanks to Almighty Allah. Though the microscope is a compound microscope. I have a great urge to look how the different cells look in the magnified form even under the compound one. And the feeling of being at the start of this journey is very much exciting.

Now lets return to the post friends. So, what do you think guys, what is this smallest and what is this largest? What can you recognize from the post tile today? These are none other than the bacteria. The smallest bacteria and the largest bacteria on earth. Does not it feel interesting to get to know about them. I was much anxious to know about them so got to do a search on them. And I got to know, the smallest bacteria is “ Mycoplasma” and the largest bacteria is “ Thiomargarita namibiensis “. Let us begin with the Mycoplasma first.


Mycoplasma is the smallest cell and the smallest bacteria living on earth having a size of about 0.2 micro meter which is about the same size as the largest virus ( poxvirus ) on the other hand. The cells varry from spherical to pea – shaped to a slender branched filament. They are mostly fluctuative anaerobes.

Mycoplasma is the name given to a group of bacteria or a genus of bacteria that unlike the other most aggressive infectious bacteria lack a cell wall. And is the kind between bacteria and viruses. They possess a flexible cell membrane containing sterols in them which allows them to take many different shapes and making them difficult to identify even under a high – powered electron microscope. It is still a question that whether the largest bacteria have evolved from the Mycoplasma or they themselves have evolved from viruses.

A large group of common  antibiotics, the beta – lactam antibiotics including the penicillins are used to kill a wide variety of bacteria that contain a peptideglycan cell wall. These antibiotics target to inhibit the synthesis of the cell wall and eventually killing the bacteria. The Mycoplasma on the other hand, not having a cell wall are not killed by these antibiotics.

 They were named Mycoplasma as some of their strains were found to have a mycelated – fungi like structure ( Mycology – the study of fungi ) with a flowering plasma like structure, hence the name Mycoplasma.

Mycoplasma species are parasites of joints and the mucous membranes lining the respiratory, genital or digestive tracts of ruminants, carnivores, rodents and humans. Mycoplasma infections in humans triggers a serious immune  reaction in the host.

Mycoplasma are often associated with chronic illness. The pathogenic species of the Mycoplasma are M..pneumoniae which causes atypical pneumonia and other respiratory disorders, M.genitalium, which causes pelvic inflammatory diseases. Some pathogenic Mycoplasma are found to involve in different cancers namely M.fermentans, M.genitalium, M.hyorhinis thought to cause colon cancer, prostate cancer and gastric cancer, and M.penetrans.Mycoplasmas also are found to cause lung cancer and renal cancer.

Mycoplasmas, unlike viruses, can grow in tissue fluids (  blood, heart, joint, chest, and spinal fluids ) and can also grow in living tissue cells without killing the cells. Mycoplasmas are also thought to involve in rheumatic diseases. Mycoplasmas are found to infect females four times more than the males.
Some other species of Mycoplasma are M.gallisepticum, M.haemofelis, M.hominis, M.hyopneumoniae, M.ovipneumoniae, etc.

If the recent studies get proved to be the case that the mechanism of Mycoplasma is both immune complex and as an autoantigen, then  soon Mycoplasma will be found to be involved in many immunological disorders such as diabetes, multiple sclerosis, etc.

Mycoplasmas appear to be unusual among other bacteria and Mycoplasma testing is very specialized and not every lab does this testing or if does, does not do it well.

Thiomargarita namibiensis

It is one of the biggest bacteria ever discovered ranging in size from 0.1 – 0.3 mm ( 100 – 300 micro meter ), but sometimes also has size of 0.75 mm or 750 micrometer. It is a gram – negative coccoid Proteobacterium found in the ocean sediments of the continental shelf of  Namibia. It is also one of the most massive bacteria.

Elaborating its name Thiomargarita namibiensis, the genus name Thiomargarita means “sulfur pearl “ which is the cell’s appearance. These bacterial cells contain microscopic sulfur granules that scatter incident light, giving the cell a pearly luster. The species name, namibiensis means “ of Namibia “. This bacterium is large enough to be visible to the naked eye.

The interesting part is that, this bigness of the bacteria creates problems for its survival. As we all know that bacteria feed themselves by simple diffusion which occurs in a rapid rate if the bacterial cell is having a large cell membrane surface area to cell volume ratio. In a big cell, like this bacterium, this ratio is lower so rate of uptake of nutrients in them by simple diffusion gets low too, allowing the bacteria to starve easily. So, is not it a problem for this bacteria? I don’t think so as they have different back up mechanism for this, which is they create large vacuoles which they then fill with the life supporting nitrates and oxygen from water. For this storage vacuoles these bacteria do not need to be in constant contact with nutrients and can also survive for a long period.

The bacterial cells are enveloped by a sheath layer which protects it from damage as a result of contact with the sediments.

The inclusion like spheres seen inside the bacterial cells are the large liquid filled vacuoles for nutrient storage already discussed above.

Thiomargarita namibiensis have adapted to its environment so well that these cells do not die due to any environmental conditions rather they may die from mutations and cell suicide, as mutations would lead to changes in their most suitable adaptations, and as a result the resulting inability to adapt to their environment after a mutation leads them to death.

About any diseases caused by these bacteria. They are actually too large to cause any diseases in humans and till now they are not known to cause any diseases in humans. They find it really troublesome to cause diseases. Most disease causing bacteria are approximately 1 micro meter across, and the Thiomargarita namibiensis are quite large to do this job.

So my dear friends, how was the journey to the world of the smallest and the largest bacteria?. I think it was quiet enjoyable, right friends. I am looking forward to share with you even more interesting news about the medical world, any new breakthroughs, innovations and some more useful information. Till than, stay healthy, be passionate and of course do not forget to visit our blog.

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