Question from a student via email

Dear MMMMM,

I have been sick these 2 days so I cannot answer your questions yesterday.

Answers

1.From question 10 in 2010 pastpaer, do we need to explain our choice of
organisms with reference to every characteristic provided? I doubt this because
the question didn't clearly state the word "Explain".

A: "Explain" means you need to put in the most relevant information explaining your choice. Only the relevant characteristic or information would be necessary and also their relevance to your choice. I donot want a whole listing of characteristics. I will probably not deduct any points from irrelevant information but you will waste your precious time in the examination.

2. Can Acetobacter species grow at 200 mV?

A: Yes. It can grow well in air.

3. What is the highest temperature that Listeria monocytogenes can grow?

A: In general, L.m. cannot grow at temperature higher than 45C.


4. Can Listeria monocytogenes grow at pH = 4.5? From your lectures, you claimed
that it can only grow when pH is higher than 5.5. However, from your previous
reply to student, you said the lowest pH allowing the growth of LM is 4.8, so I
am wondering whether it can grow at pH = 4.5.

A: Growth limits depend on many factors. In general, L.m. cannot grow at pH below 4.8. But some reports stated that L.m. can grow down to pH 4.1. It can be confusing. But it usually does not grow significantly below pH4.5.

Best,

HS Kwan



-----Original Message-----
From: MMMMMM
Sent: Sat 5/4/2013 11:32 PM
To: hoishankwan@cuhk.edu.hk
Subject: Questions about FNSC4180

Dear Prof. Kwan,

Sorry to bother you again. There are some questions remained unclear for me, may
I have the answers?

1. From question 10 in 2010 pastpaer, do we need to explain our choice of
organisms with reference to every characteristic provided? I doubt this because
the question didn't clearly state the word "Explain".

2. Can Acetobacter species grow at 200 mV?

3. What is the highest temperature that Listeria monocytogenes can grow?

4. Can Listeria monocytogenes grow at pH = 4.5? From your lectures, you claimed
that it can only grow when pH is higher than 5.5. However, from your previous
reply to student, you said the lowest pH allowing the growth of LM is 4.8, so I
am wondering whether it can grow at pH = 4.5.

Thank you very much.

Best Regards,
MMMM

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