Posts Tagged “bacteria”

“Get me more, mummy!” demands one youngster bacterium, pointing to the drops of antibiotic reaching the colony headquarters.

Come on! FOR REAL?

Sadly very true and it is not even that infrequent either! I only became aware of this after reading about a study, where researchers in HMS, led by Dr. George M. Church, collected soil samples in an experiment, attempting to search for more bio-diversity and were stunned to see that as they added antibiotics to these bacterial cultures, the bacteria didn’t seem to mind at all!

Unlike human beings, bacteria tend to like sharing. The more they share their strategic defenses, the more prosperity they end up living in. Again, to our dismay, such fear was translated into reality, as this has already extended to the pathogenic minorities of the bacterial world in a new study, published in January in the International Journal of Tuberculosis and Lung Disease. Scientists, in China, have stumbled upon a strain of tuberculosis-causing bacteria, called Mycobacterium tuberculosis, INCAPABLE of growing adequately in the absence of rifampicin. This is as ominous as such news can get.

This strain was discovered as physicians attempted to treat a TB-infected patient with a regimen which included rifampicin. Unexpectedly, his condition worsened and only upon the removal of rifampicin did he start feeling better, until eventually full recovery. Already, reports of multidrug-resistant TB “MDR” have been around for some time. Normally, the treatment course includes more than 1 drug to be able to effectively kill the bacteria. Apparently, the bacteria have found a way to get around that!

We can only wonder: which antibiotic is next?

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Did you see some one before who can fly without wings or move without legs? You will answer : definitely no, but I know someone, or better yet some living thing, who can do just both and it is called Borrelia burgdorferi; let’s share its story. It is a loosely coiled bacterium belonging to a class called spirochetes (moving bacteria).

Borrelia burgdorferi

Borrelia burgdorferi

Borrelia burgdorferi is motile through the undulation of its axial filaments. It is transmitted to humans by the bite of infected ticks (Ixodes scapularis and Ixodes pacificus) and cause a serious progressive disease called lyme disease.

The story of lyme disease began in 1975 when a mother, with her children in lyme city in the United States, was admitted to a hospital with signs of rheumatoid arthritis. It was a mysterious case until the discovery of Borrelia burgdorferi and that is how the disease got its name, when it was discovered in 1982. Symptoms and signs of lyme disease can be categorized into three phases:

Phase (1): An early localized skin rash, characterized by inflamed red edges with a clear white center at the site of insect bite, appears and is called “erythema migrans“.


Erythema migrans

Phase (2): The rash resolves as the bacteria begin to move into the blood stream towards their target organs like large joints, heart, and nervous system.

Phase (3): Inflammation of heart muscle leads to abnormal rhythm, meningitis, confusion and finally arthritis.

Treatment in the early phase is an easy mission by amoxicillin or doxycycline, orally for few weeks. However, the recommended regimen in late stages include parenteral ceftriaxone, analgesics to control the severe pain, and anti-inflammatory drugs, usually required for months .

Images credits:
Borrelia burgdorferi:
Erythema migrans:

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Researchers at Yale & the University of Chicago were faced with a surprising conclusion based on their scientific experimentation on mice. Unlike the common belief that microbes are in fact “bad” & possess a harmful threat to our health, some of these bacteria prove their innocence. Mice, that were exposed to common bacteria in the normal gut flora, were protected against the development of Type I diabetes. Previous research had shown that mice, exposed to killed Mycobacterium tuberculosis, were also protected. So, this means that mice that grow in their natural habitat are better off than the ones raised in the much improved sanitary conditions of the lab.

This comes to support the hypothesis many scientists have lately adopted. They tend to believe in a directly proportional realtionship between a person’s exposure to parasites, bacteria, worms, etc.. within the surrounding evironment and his immunity. The more, the better..that is within limits of course.

This actually makes perfect sense to me. It is really obvious when you see, for example, people living in third world countries with mosquitoes hovering around and considered normal. But when they travel abroad for a while and come back, they get different sorts of allergies & rashes from those previously “harmless” mosquitoes. What parasites and microbes do for you is not all bad. Unfortunately, I had to experience this dilemma.

Source: ScienceDaily

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Recently, I have been able to get in touch with Professor Jan Roelof van der Meer after reading about his work in EurekAlert in the field of color-coded bacteria. Currently, he is an associate professor at the Department of Fundamental Microbiology, University of Lausanne.

In a review published in collaboration with Professor Robin Tecon, the researchers explained why the bacteria were specifically useful in the detection & tracing back the age of oil spills, chemicals and other pollutants leaking into seawater and the soil. Since the bacteria are easily manipulated, researchers were able to genetically produce MBS “Microbe-Based Sensors” which produce specific reporter proteins when in contact with a certain pollutant. Such reporter proteins can then be detected merely by observation or instrumentally.

Enclosed within the review, this figure illustrates the concept of a bacterial sensor-reporter cell where the benzene-ring-look-a-likes represent the pollutants.

And I leave you with the interview:

1. Is there hope that MBS won’t just play a role in detection, but in cleaning up as well?
Normally not. To enhance biodegradation rates in the environment, one usually tries to stimulate the bacteria which are already present at the site. There are no cases where genetically modified bacteria were applied to clean up contamination.

2. How can this method trace back the age of a spill?
Interestingly, we found that there seems to be a specific pattern of dissolution of different compounds from oil. A fresh spill will first ‘show’ linear alkanes and compounds like benzene, toluene, ethylbenzene. Only later will polycyclic aromatic hydrocarbons, like naphthalene, appear. We had not seen this before, because one typically cannot measure the first phase of an oil spill, since this is detected only after a while.

3. Which method do you prefer in the genetic engineering of these MBS?
Depends. For E. coli, we use very classical cloning techniques involving plasmids. For other bacteria, we have to use transposon delivery methods mostly.

4. Is the acquired trait of producing a reporter protein passed on to future generations of the bacteria?
Normally yes. If the reporter construct is integrated in the genome of the bacteria, it is relatively stably maintained even without selection pressure for the marker. When the construct is on a plasmid, like in E. coli, one has to constantly keep the ‘pressure’ for the marker on the plasmid, usually an antibiotic resistance marker.

5. This field, as you kindly mentioned, started 20 years ago; what hope lies for its progess in the future?
My major hope is that people (industries, labs) finally apply the methods in their analysis as alternatives for costly chemical analysis. Further progress has to come from miniaturization, multiple target detections and improved methods to preserve the bacterial cells.

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It is something like a dream, Marijuana, which is known in Egypt as “Hashish “, is used now as an antibiotic.

Marijuana is a herb planted in many countries as middle east eastern, Europe & Africa.

It is ingested by smoking, which quickly delivers active ingredients to the blood system. Marijuana has analgesic, anti-emetic, anti-inflammatory, sedative, anti-convulsive, and laxative actions.

Also, it is used in chemotherapy to relieve nausea & vomiting and for AIDS patients as stomachic.

Scientists tested five major active ingredients called cannabinoids on Different strains of MRSAmethicillin resistant Staphylococcus aureus“.

Both natural & synthetic cannabinoids show germ killing activity against MRSA.

These active ingredients exhibit antibacterial activity in a different way, meaning that they might be able to bypass bacterial resistance.

At least two cannabinoids “out of 5″ can be used safely without causing mood alteration.

MRSA like other Staphylococcus spread by contact, so people of close contact are of high danger.

Finally, researchers in the Journal of Natural Products call for the further study of antibacterial uses of marijuana as it is too difficult to find new antibacterials since unfortunately, bacteria became resistant to them.

Source : Web MD

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Scientists have found out that alligator blood is able to fight different kinds of bacteria including even MRSA “Methicillin-Resistant Staphylococcus aureus“. This is due to the presence of several peptides within the alligator’s blood which pose as a natural barrier against bacterial infection. This particularly comes in handy since alligators are known to live in conditions very preferrable for the growth of microorganisms, mainly in swamps to be exact.

The idea first struck Dr. Mark Merchant when he noticed that despite of their habitat, alligators seem to strive quite normally with scratches & bruises in their skin. Researchers then isolated an alligator’s serum & did a comparative analysis against human serum. Out of 23 strains of bacteria, human serum was able to conquer only eight, while that of the alligator’s stood undefeated against all 23. Not just that, but the serum was also tested on HIV & surprisingly, a great amount of the virus was also destroyed.

Surely, the benefit of this discovery would arise once those peptides are sequenced & their exact chemical structure identified to manufacture them in labs as it would be pretty unreasonable in terms of animal rights AND cost-wise to slaughter alligators for their blood.

Drugs containing these peptides are expected to become available within the next 8-10 years & would definitely prove very useful for patients highly vulnerable to infections as in certain autoimmune diseases, diabetes, burn victims and those with open surgical wounds.

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Nature, mother nature & the famous journal, taught us that every organism has its own defense mechanisms against various predators. For example, the famous antifungal agent (cyclohexamide) is obtained from the bacteria Streptomyces, on the other hand (Penicillin), the antibiotic, comes from the fungus Penicillium.

We all know phages, the nick name of Bacteriophages, the virus-like agents that infect bacteria making it sick.. Well not sick, but only degrade it like any other virus on the planet. As a matter of fact, Bacteria have to develop defense mechanisms against these phages:

1)They can cut their genome with restriction enzymes (endonucleases)

2)They can also undergo changes in their receptors, so the phage goes blind & never find it

3)They can act on the phage itself by making DNA modifications or even repression of their gene expression.

But now we’ll talk about a different defense mechanism (they love to call it: Special Forces). To know it, you’ve to meet CRISPR sequences (clustered, regularly interspaced, short, palindromic repeats). Not crispy, it’s CRISPR. Actually when I first read it, I was totally lost. I knew the meaning of every word separated from the very next. So I checked more & got this from the amazing blog of Tim “Phage Hunter“.

As you’ve read before, they are sequences found in almost 40% of sequenced bacteria & 90% of sequenced archaea. There are already identical repeats which form RNA stem-loops. Between those repeats, researchers found DNA which is similar to that of phages. That means that the bacteria use the RNA interference mechanism (an inhibitory gene expression mechanism).
CRISPR sequences are first transcribed, and then spliced to form small interfering RNA (siRNA), which are complementary to the target mRNA (the phage’s). Once binding achieved, no translation occurs, because they simply cleave it into little pieces.

Bacterial CRISPR is modeled to work as iRNA in eukaryotes

So the array of these sequences is highly useful in determining the bacterial resistance to different phages. Y. pestis (aka Black death) has three CRISPR sequences in its genome. It’s something like acquired immunity, bacteria develop it after the infection of the phage, the survivors of course.

For people On The Run: Bacteria have a complementary sequence of their phages, to capture their RNA, stop the translation process.

Image credits:
Figure shows the role of siRNA in degradation of phage nucleic acids:

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