Questions in General Microbiology - Ask the Expert

March 16, 201116comments

Ask your questions in General Microbiology in the comments section and get clarified from your query by our experts in the specified discipline.

Interesting questions along with answers will be published in comments section as early as possible.

The viewers are requested to restrict the question to General Microbiology, since questions regarding Immunology, Bacteriology, Virology, Mycology and Parasitology are posted as separate.

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Anonymous
March 23, 2011 at 8:57 AM

my question is that when we use any antibiotic it kills the pathogenic bacterias but does it effects the bacterias present in our intestine like Escherichia coli

March 23, 2011 at 11:29 AM

Answer to a question asked in comment No.1:

It is obvious that the oral intake of antibiotics and chemotherapeutic agents have an adverse effect on the normal intestinal flora. So, the current trend is moving towards the use of probiotics(oral microbial supplements) in addition with antibiotics to re-establish the normal flora.

Moreover, the use of broad spectrum antibiotics are not recommended owing to the risk of antibiotic associated diarrhea caused by Clostridium difficile.

Nauman
May 11, 2012 at 11:24 AM

Can you please translate this is simple words , i am not a student of biology but have been asked to read a Nature paper , these are lines from it

Parkin is recruited selectively to depolarized mitochondria and directs mitophagy. HeLa cells transfected with HA-Parkin were treated with CCCP for the indicated times( there was a figure in which times were indicated). Mitochondria were stained by anti-TOM20 and a mitochondrial membrane potential-dependent Mitotracker. Parkin was stained with anti-HA. Without treatment mitochondria are intact and stained by both mitochondrial markers.After 2 hours of CCCP treatment, mitochondria are depolarized as shown by the loss of mitochondrial staining. After 24hr of CCCP treatment, massive loss of mitochondria is observed as shown by the disappearance of the mitochondrial marker. Only parkin positive cells show mitochondrial clustering and clearance, in contrast to transfected cells.

May 11, 2012 at 3:14 PM

It is difficult to translate the contents in simple words...

But it would make sense if you read the paragraph as


Parkin gets selectively recruited to depolarized mitochondria and directs degradation of mitochondria.

HeLa cells transfected with HA-Parkin were treated with CCCP for the indicated times.

Mitochondria were stained by anti-TOM20 and a mitochondrial membrane potential-dependent Mitotracker and Parkin stained with anti-HA.

Mitochondria not treated with CCCP are intact and are stained by both markers. After 2 hours of CCCP treatment, mitochondria are depolarized as observed by the loss of mitochondrial staining. Post 24 hours CCCP treatment, there is massive loss of mitochondria observed, as shown by the disappearance of mitochondrial marker.

In contrast to transfected cells, only the Parkin positive cells show mitochondrial clustering.

August 12, 2013 at 4:11 PM

Dear Scientist

my name is Xueling Li. I am a master student in the University of Hohenheim, Stuttgart, Germany.

with this email, I would like to ask you kindly about the kit that I need for my master thesis.
here as follow is the information about my desirable test;

1. I am using Eugenol as my antimicrobial agent. The bacteria that I used are Staphylococcus carnosus and E. coli K 12.
2. I would like to see the resistance of these 2 bacteria against Eugenol.
3. Hence the Eugenol antibacterial mode of action is by destroying the cell membrane of these bacteria.

My question is: Do you have a special kit (simple one, not like the big machine)
in your company for my requirement to detect certain resistance expression? if yes, how can I order it?

Thank you for your kind of help and attention and I am looking forward to hear from you soon.

Kind Regards,
Xueling Li

Anonymous
December 30, 2013 at 10:11 AM

Back in 2003 I traveled to Arizona. I stayed for a few months. One morning I noticed a floater. However unlike the normal floaters that one experiences in one's eye, this floater is different. The floater I am experiencing actually has a head, with a visible eye. It has a tongue, which is split. It has a hinged body. And it has a split tail. Almost like a little parasitic dragon. What the hell is this? And how do I get rid of it?

April 24, 2014 at 6:19 PM

@ patricia bianca

I apologize for this delayed reply & Thanks for your question.
If you are still searching the solution, please send us little more detail;
Phenotypic resistance could be simply detected by diffusion/dilution methods.

June 16, 2014 at 7:27 PM

Some times when i autoclave d media, agar in d media does not melt completely. Whay must be d problem?
by KP Vaibhav

It may happen due to any one of the following reasons; You have to find our which one is your problem:
1. Improper mixture of agar and media ingredients (problem with manufacturer; as you mentioned it happens only some times, it may not be a problem with manufacturer)
2. According to the standard procedure - you have to melt the agar before autoclaving; however most often it is not practiced.
3. Inadequate mixing of media in distilled water (manual error)
4. Autoclave temperature may not achieve 121C (have several reasons) or holding time may be less than 15 minutes
5. If you are preparing >500ml of media in single container you have to increase the holding time accordingly.
6. Your media container may not allow the penetration of steam (use cotton plug; don't use aluminium foil to cover your container).
7. Don't dump your autoclave completely.

Hope this will help you to solve your problem. Thank you.

November 14, 2014 at 6:18 PM

@ travis7984

Fungi can be either unicellular yeast or multicellular mold.

To your second question, not all organisms are predatory, for example algae are photoautotrophs (takes CO2 as a source of carbon and light as a source of energy) and they do not feed on another organism. But only viruses are obligate intracellular parasites and always exhibits parasitism on another organism.

In terms of parasitism, size doesn't matter; for example a dengue virus which is just few nanometer in size, bat are capable to kill a human measuring 2 meter in size - it is associated with pathogenicity i.e., disease producing ability.

February 28, 2015 at 6:37 PM

@Julie Scanlon
Possible reasons for non-motile E.coli under wet mount preparation are,
1. Wet mount is not recommended for the examination of bacterial motility - Hanging drop technique is recommended
2. Old culture/ depletion of nutrients/ accumulation of toxic metabolites/ etc.,
3. Presence of H antibodies or any chemicals that have an antimicrobial action.

April 24, 2015 at 3:49 PM

Query/Message: Hi There! I have been searching for the answer for the following question but I can't find it. The question is simple: why does the yogurt container bulge when it goes off? Is it because of heterolactic fermentation, producing CO2 plus ethanol and lactic acid? I have read that the main cultures for making yogurts are Lactobacillus bulgaricus, L. acidophillus and Streptococcus thermophilus, apparently not heterolactic. Do other bacterias colonize the mix? Thanks a lot for your answer. Rafa- Spain

The probiotic bacteria added for lactic acid fermentation in yogurt/curd preparation are not gas producers. The presence of gas producing bacteria (bulging of container) in yogurt indicates contamination with unwanted bacteria. It may or may not be harmful to the consumer depending on the pathogenicity/toxigenicity of the contaminant.

May 4, 2015 at 11:38 AM

Our project is to ID 2 unknown gram - enterics to genus and species. My EMB agar shows metallic green colonies, so I believe it's E. coli. My HE agar shows bluish-green colonies with no black precipitate, so I believe it's Shigella. If this media is selective and differential, why do I need additional testing? What tests would you recommend? Thank you!
- Dark Blue Dreams

Identification by selective medium is always presumptive (i.e., some other microorganisms may also give similar picture - for example citrobacter/enterobacter on EMB) and requires confirmatory identification. E. coli can be better identified with biochemical tests and Shigella can be better identified with agglutination test with specific antiserum or you may use molecular techniques for confirmation.

May 18, 2015 at 6:49 PM

Can you please tell me if the toxins produced by the Clostridium Botulinum bacteria are themselves living organisms possessing their own DNA or are they merely dead chemicals? Your help in this matter would be greatly appreciated. Thank you.
Malcolm Reid

Botulinum toxin is not just a chemical - it is a nerurotoxic protein encoded by an indigenous gene (chromosomal gene) of Clostridium botulinum.

November 11, 2015 at 8:43 PM

Hello, I am Olu. Could you kindly clarify why the below statement is so, as I am confused :

10 to power 1 cfu has a max acceptable count of 20
10 to power 2 cfu has a max acceptable count of 200
...and so on. I thought it should be 10 and 100 respectively.
Please clarify
Thank you

Colony counting is based on probability, in which 10% buffer is always acceptable.
For example, the acceptable colony count is expressed as 10^2
the next criteria is 10^3 not in between
Hence, the 10% buffer will felicitates whether to put the specimen under 10^2 (fit) or 10^3 (unfit).

November 19, 2015 at 1:47 PM

on refering few papers i came up wit a small project.. in that i am supposed to get a zone of growth around the plated wells in a media which is MEM wit a carbon source.. as per the references... but i have got growth of colonies.. but not a zone of clearance.. so how can i conclude it? has the organism not degraded that carbon source to form a zone of clearance and has it just utilised tat carbon source to grow? is that possible? please explain..
thanks in advance


I could't understand your question. Please make it clear.

Readers are advised to ask their question unambiguously with proper explanation; cite appropriate references if it is necessary for understanding.
Thank you.

November 19, 2015 at 1:47 PM

on refering few papers i came up wit a small project.. in that i am supposed to get a zone of growth around the plated wells in a media which is MEM wit a carbon source.. as per the references... but i have got growth of colonies.. but not a zone of clearance.. so how can i conclude it? has the organism not degraded that carbon source to form a zone of clearance and has it just utilised tat carbon source to grow? is that possible? please explain..
thanks in advance


I could't understand your question. Please make it clear.

Readers are advised to ask their question unambiguously with proper explanation; cite appropriate references if it is necessary for understanding.
Thank you.

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