# Bacteria culture

### #1

Posted 31 July 2009 - 12:19 AM

I carried out an experiment and got my bacteria to grow from (3.56 X 10(7)) to (8.5 X 10(8)) in 11 hrs.

My question is that if I half the initial inoculation amount, will it take double the time to reach the same number of bacteria? That is if I inoculate(1.78 X 10(7)) number of bacteria into the medium, will I get (8.5 X 10(8)) bacteria after 22 hrs?

### #2

Posted 31 July 2009 - 01:25 AM

**Edited by dreww, 31 July 2009 - 01:31 AM.**

### #3

Posted 31 July 2009 - 03:40 AM

Just a quick question,

I carried out an experiment and got my bacteria to grow from (3.56 X 10(7)) to (8.5 X 10(8)) in 11 hrs.

My question is that if I half the initial inoculation amount, will it take double the time to reach the same number of bacteria? That is if I inoculate(1.78 X 10(7)) number of bacteria into the medium, will I get (8.5 X 10(8)) bacteria after 22 hrs?

Need to do a growth curve. Because bacteria can grow exponentially, it may only take 1 hour long to reach that number if they can replicate in 1 hour...

If you add half the inoculum and they replicate one time per hour, in one hour you will have already made up that difference.

Inoculum can be tricky, which is why I say do a growth curve. Start with different inoculums of a standard culture. For instance, do an overnight (16 hour culture), then use that to inoculate 50 mls. Inoculate 50 ul in 50 mls (1/1000), 100 ul (1/500), 500 ul (1/100), and 1000 ul (1/50), then take OD readings every few hours to see how well it grows.

With the bacteria I work with, I can get a 7x10^9 cfu/ml in 16 hours from a 1/100 inoculum. However, if I do a 1/1000 inoculum, I hardly get anything grown in 36 hours.

### #4

Posted 31 July 2009 - 07:54 AM

so I inoculate 50 microlit of OD 0.922 culture into 1ml and got the OD after 11 hrs...

This time Im trying to scale up to 100ml and I want it to reach the same OD in 48 hrs...

So I thought maybe if I half the initial amount I might get to the OD in 48 hrs..

By the way I have carried out enumeration so I know the exact number of bacteria corresponding to the OD

### #5

Posted 31 July 2009 - 08:43 AM

### #6

Posted 01 August 2009 - 05:12 AM

Sure agree with pernese - scaling up will change dynamics so you can't accurately predcit the effect on growth rates. I also wonder at the excessive precision reported.