# Gamewizard

Senior Members

135

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• Birthday 02/27/1989

## Profile Information

• Location
England, London
• Interests
• College Major/Degree
MSC Biomedical Science :)
• Favorite Area of Science
Microbiology/Human physiology/Diseases
• Occupation
Part time student

• Quark

11

1. ## T-test question

Hi, Simple question, Can a standard T-test be used for two sets of data which has about 5 values ? I am trying to find diffrences in growth between two bacterial strains at a certain temperature , i was going to do the T-test but i read somewhere that a t-test needs atleast 10 values in your data sets.
2. ## Optical density = concentration

Thank you for your replies, I will have to do plate counts for it
3. ## Optical density = concentration

Hi quick question What would be the bacterial concentration at 0.6 OD ? and how would you write that as ? thank you
4. ## Determining MIC

Hi all I basically need some help with interpreting my MIC results. I have carried out a MIC test on some raw materials against my bug. Bacterial inoculum was at 0.6 OD. Used a 96 well A to H microtire plate. Obviously made serial dilutions of the raw materials, now some of my raw materials were liquid so i used them straight away (100%) but some were solids so i had to dilute them first with with sterile water. I made a 1 in 2 dilution so put in 10g of solid raw material in to 20 g water. So thier starting percentage was 50%, and then the serial dilutions were made from Column 2 (total vol of column 2 was 200ul as i had 100ul sterile water and 100ul of raw material in it) by taking 100ul out and transfering to next one and so on. (1 in 2 dilution so the percentage was halved each time like so):- Raw material A 100%, 50% 25% 12.5%, 6.25%, 3.125%, 1.5625%, 0.78174%, 0.390625%, 0.1953125%, 0.09765625%, and 0.0244140625% for all wells. Now i need to determine at what concentrations the raw materials inhibited the bacterial growth and I dont know how to figure out the concentration, and i believe the concentration has to be in ug/ml as well ? Can some one please help me figure this out, I have looked on the internet but it has confused me and I do not understand it. Thank you for reading
5. ## Measuring pH of bacteria

I have had a chat with someone, and they suggested I try adjusting the pH of my LB broth with simple citric acid alone ? do you think that would work ? and if I wanted to bring the pH up do you think it would be okay to use NaOH ? and just keep measuring with pH meter until the broth is at desired pH ?
6. ## Measuring pH of bacteria

Yes I understand what you mean. I will have to take in account that, however what I dont understand is if I was to make a buffer solution at pH of 3.5 (Citric acid buffer) how will i do that ? and then do I add the prepared buffer at that pH to my liquid media to make the media at 3.5 pH and then measure growth of bacteria from there? and how much bacteria will i be inoculating ? i am trying to do find some papers who have done this or even just simple method from a site etc but i cannot find anything So for example I have now found out that to make citric acid buffer at pH of 3.5 (mM 50) I need 0.7119% w/v citric acid and 0.3807 %w/v sodium citrate, but how do i calculate this in grams ? and how do i know it is 50mM
7. ## Measuring pH of bacteria

Hi, Not sure if this should be in homework help ? I need to test pH levels of an organism, basically to find out at what pH it grows best, where it stops etc. I have decided on a pH range. I intend to use LB broth/BHI as the growth medium for bacteria (in which i will inoculate my bacteria). (My bacteria is from Enterobactericiae, closely related to E.coli) The pH range i am going for is 3.5, 4.5, 5.5, 6.0, 6.5, 7.0, 7.5, 8. I know certain buffers which are capable of maintaining these pH ranges, and that I can also adjust the pH with NaOH and HCl. But I do not know how I will make my media with these specific pH levels using buffers and how I will maintain them (keep them at same pH) because I have read that pH decreases as bacteria grows. Citric acid buffer can be used for making pH of 3.5, 4.5, 5.5, 6.0. MES buffer solution can be used for making pH of 6.5 HEPES buffer solution can be used for making pH of 7.0, 7.5, and 8.0 Adjust pH with NaOH or HCl Any ideas on how I can carry out this experiment?
8. ## calculating concentration from %

Hi how can u calculate concentration of a solution from its percentage ? for example if i had a 50% solution, how will i calculate its concentration ? (i have made that 50% by diluting it 1 in 2) or is it the same thing ? thank you
9. ## Urgent help needed

Sorry, yes they are all w/w %
10. ## Urgent help needed

Hi I am making a formulation and i dont know how much water to add in there. The base mixture is is 2000g in total, and has 736.716 g of water (% w/w is 36.8358) I need to make the mixture to be 5% of a raw material, 6% of a raw material, and 8% of a raw material. I have calculated how much raw material i need to add in grams for example, 5% of raw material A mixture will contain 100g of material A, but i am having problems with calculating the amount of water i need to add to each of these % mixtures. can anyone help me help calculate the amount of water in grams i need to add to the 5% mixture ? help please

because 1/100 is 0.01 ? am i right

Hi so my question is basically on dilutions which I need to do for carrying out an MIC test in microbiology a 1 in 10 dilution converted to percentage is 0.01, a 1 in 100 dilution is 0.001, however if I had a 1 in 10 dilution in my microtitre plate well A1 in which I have added 1ml of bacteria and 9ml of water, how much would I be taking from this first well to the second well to make it 0.06% ? and how much sterile water would I be adding ? and also is 0.06, a 6 in 100 dilution ? please help confused !
14. ## Colony count help

Hi, So i have made some serial dilutions and counted my colonies from two plates (replicate plate also) taken the average and that is 30. These plates were from my 10^2 dilution. Overall i had made 7 dilutions from 10^8 to 10^1, and total dilution is 1 in 10. The vol i plated on to the agar plates was 1ml. So to get CFU per ml in in the original stock solution (10^8), I need to use this formula which is Colony count per plate x dilution factor /vol plated. However, when it says dilution factor do they mean the total dilution factor which is 1 in 10? or the dilution of the actual plate which is 10^2 ? Can someone please just clarify this, I have looked endlessly on the internet and no where does it say Thank you

Thank you everyone for your help, I have got it now
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