Thread: Microbiology Questions...HELP

Hey guys I'm new to this forum and I need help! I'm answering some micro questions for uni and I have a few questions I can't answer (I've tried looking for answers everywhere!) They might be stupid questions and I'm not exactly the smartest person so here goes....

1: Explain how bacteria can grow large colonies on starch agar but not necessarily produce amylase.


2. DNases are too large to be taken up by cells, so they would not be effective against DNA within cells. What do you think is the source of DNA when these organisms are in their natural environment?

3. Some pathogens produce proteases and lipases. How might these enzymes contribute to their ability to cause disease?

Sorry, your questions are very good,
1 The only real way to determine if a bacteria produces an enzyme if it secretes exoenzymes, so maybe those bacteria produce endoenzymes??

2 you are assessing if your organism is able to secrete exoenzymes which break down DNA, making it SMALL and SOLUBLE, which allows the bacteria to take it up and use it to make more DNA??

3proteases and lipases in the body are at a balance aren't they, if those pathogens start making more, fats etc will be broken down before they can be used, leading to a form of malnutrition???

Maybe that was no help, but I thought I might as well try :P see ya around, 9maybe someone will be angered by my post and post the right ones??!!) lol, bye!!

Thanks for replying!! They're very hard questions...come on people! Is there no one else??

1: Explain how bacteria can grow large colonies on starch agar but not necessarily produce amylase.

The bacteria secrete the amylase and it degrades the starch outside of the cell. Therefore not every bacteria needs to produce the amylase to benefit from it!

2. DNases are too large to be taken up by cells, so they would not be effective against DNA within cells. What do you think is the source of DNA when these organisms are in their natural environment?

I'm not sure what you are asking here. When you say "DNases" are you referring to the enzyme that degrades DNA or multiple DNA molecules? I think perhaps you have the wording on this question wrong because its not making any sense to me.

3. Some pathogens produce proteases and lipases. How might these enzymes contribute to their ability to cause disease?

Proteases degrade proteins and lipases degrade lipids. Both of these molecules can cause some serious damage to a cell if their activites go unchecked! I would speculate that the pathogen would have markers on its lipids/proteins so that it could secrete these enzymes and destroy host lipids and proteins. The pathogen could then use the amino acids and fatty acids produced from this to divide and conquer!

There you go, people replied !!

2. DNases? enzymes to break it down? Not sure but, do viruses have those? if that's the case, they wouldn't need to permeate through the cell, cause viruses inject them. The theme seems to be bacteria though...Sorry that can't be any real help

2. DNases? enzymes to break it down? Not sure but, do viruses have those? if that's the case, they wouldn't need to permeate through the cell, cause viruses inject them. The theme seems to be bacteria though...Sorry that can't be any real help

Most viruses can inject their DNA or RNA into the cell and the cell's replication/transcription machinery will take it from there. Some times the virus will even place itself into the cells genome and wait there for a better time to replicate itself hundreds of times and kill the cell.

Cells use DNAses as a part of the apoptosis mechanism.

Lateral gene transfer between bacteria usually takes place via plasmids. These are short circular molecules of DNA that contain just a handful of genes. These plamsmids usually remain seperate from the bacterial chromosome and are usually present in high copy number (10s to 100s or even 1000s per cell).

These are secreted into the bacteria's environment or are released when a bacterium is lysed. Plasmids are readily taken up by other bacteria as they often contain genes which are benificial. So this is a common mechanism of gene transfer that does not involve DNAse cutting of bacterial chromosomes.

This may also be what the first part of the question is getting at. Maybe the bacteria cells themselves do not naturally express Amylase but they have acquired a plasmid which contains this gene?