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
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.
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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