Calculating Bacteria Population?

Let's assume that bacteria can reproduce once every 20 minutes during binary fission. Assume further that his rate of reproduction can be maintained. Now, calculate how many bacteria there would be after 1-hour period if you started with a single bacterium

Calculating Bacteria Population?
Bacterial growth





In this section we will return to the questions posed in the first section on exponential and logarithmic functions. Recall that we are studying a population of bacteria undergoing binary fission. In particular, the population doubles every three hours.





We would like to know the following:





How many bacteria are present after 51 hours if a culture is inoculated with 1 bacterium?





With how many bacteria should a culture be inoculated if there are to be 81,920 bacteria present on hour 42?





How long would it take for an initial population of 6 to reach a size of 12,288 bacteria?








http://www.biology.arizona.edu/biomath/t...











Exponential Population Growth


Tutorial to help you answer problem 1.


How many bacteria are present after 51 hours if a culture is inoculated with 1 bacterium? Use the model, N(t) = Noe kt, and assume the population doubles every 3 hours. (N(t) is the population size at time t and k is a constant.)





Tutorial





Now that we have convinced ourselves that an exponential model is appropriate, but not perfect, we will use the general model





N(t) = N0e k t (1)


where N (t) represents the population size at time t (Note: you may also use the model, N (t) = N0a t ). The question asks for the population size when t = 51. In order to use this model, we will need to figure out the values of the constants, N0 and k. At time t = 0, there is a single bacterium, therefore N0 = 1. Substituting N0 = 1 into (1) gives,


N(t) = 1 ⋅ e kt = e kt, (2)


We now use the fact that when t = 3, N(3) = 2 (the population has doubled). Substituting the point (t, N(t)) = (3, 2) into (2),


N(3) = 2 = e 3k (3)


We can now solve for k in (3) by "undoing" the exponential using the natural logarithm,








Using this value of k our model in (2) becomes,


(4)


Now that we have our model, we need to find the population size after 51 hours. Substituting t = 51 into (4) yields,








Thus, we find that after 51 hours there are 131,072 bacteria.
Reply:follow the formula: 2n


so if you start with 1 bacterium and replicates every 20 mins that means that in 1 hours there will be 3 replications therefore


2(3)=6


there will be 6 bacteria

1. Bacteria reproduce asexually, through binary fission. then how???

1. Bacteria reproduce asexually, through binary fission.





and how, then, does genetic variation arise in a population of bacteria?





does genetic variation within a bacterial population lead to antibiotic resistant strains?

1. Bacteria reproduce asexually, through binary fission. then how???
%26gt; and how, then, does genetic variation arise in a population of bacteria?


a) Through mutation.


b) Through the presence of plasmids that may not be in every individual.


c) Through the presence of genes brought in by lysogenic viruses.





%26gt; does genetic variation within a bacterial population lead to antibiotic resistant strains?


The antibiotic resistant strains are generally those that have a plasmid with genes that enable them to deal with the antibiotics, so, yes.





=


Bacteria can send a copy of a plasmid, and even bits of their chromosome, through bacterial conjugation. Look up "sex pilus" and "pilus receptor." With the right pilus and receptor, even bacteria of completely different species can conjugate with each other.
Reply:Genetic variations must arise through mutations, unless I'm missing something.


Yes, genetic variation leads to antibiotic-resistant strains of bacteria. The antibiotics kill off all the bacteria that are susceptible to it but can't kill the bacteria that is resistant to it. That strain of bacteria is left to reproduce and the antibiotic-resistant strain becomes the dominant bacteria.
Reply:Genetic variation occurs through mutations and through gene splicing, though the latter isn't natural.





Bacteria can also exchange DNA with other bacteria, I beleive this is called conjugation.
Reply:Mutations and conjugation. Sometimes the bacteria screws up its own DNA in the copying processes and they can exchange DNA from other bacteria.
Reply:Generally bacteria reproduce by binary fission, and sometimes a mutation occurs. Most mutations are deadly, but some are not.





But bacteria can conjugate with another bacteria and exchange genetic material, they do this occasionally. This is how antibiotic resistant strains occur.

lady slipper

Can bacteria live and grow in inorganic material such as clothing?

For instance, will the blood stained clothes a butcher wears, continue to harvest bacteria even if he (hypothetically) does not get more blood or new bacteria into his clothes?

Can bacteria live and grow in inorganic material such as clothing?
Nearly everything has a bit of organic matter on it from dust etc. Combine that with a bit of moisture and some bacteria can live.





Clothing is however usually organic (cotton, wool, silk, leather etc) and there may be enough nutrients there for some bacteria to grow given just a tiny bit of water. Some of the synthetic fibers such as nylon even can be used as food by some specialized (but rare) bacteria.





Clothing in general also usually has dead skin cells, sweat etc from our bodies and that is enough organic matter for bacteria to live on.





As for not geting new bacteria on an article of clothing. That is just about impossible outside of a clean room or a sterilized box. I seriously doubt any clothing that touches bare skin can be kept bacteria free. (regardless of how much the person just washed).
Reply:Blood is organic material - so your example doesn't fit your question.


There are plenty of bacteria that are photosynthetic, and therefore produce their own organic material to survive. - Therefore, yes!
Reply:I doesn't take much for bacteria to grow...in your example , yes it will continue to grow!

Which bacteria are most deadly?

what type of bacteria are most deadly ?





where can the bacteria be found ?

Which bacteria are most deadly?
E.coli - Spinach


Salmonella - Tainted food from china


Antrax - Letters from Osama
Reply:the one which kills you !!!!!!!!!!

Aquarium bacteria cycling question for experts?

I recently started a tank, after not doing fish for a few years. My ammonia has gone down to zero . That is testing just before the daily water change. The nitrite and nitrate are a different story. They have been stuck at 2 ppm %26amp; 20 ppm, respectfully. They have been this high for several weeks. This seems high to me, even for cycling my tank, but I don't think I should get rid of it ALL. Wouldn't that make the bacteria for the nitrite die or at least not multiply? Also What level should I try to keep them at? I understand zero is the target but what about during your initial cycle? Am I wrong in thinking that I want to have a little bit left in there to encourage bacteria growth?








Thank you.

Aquarium bacteria cycling question for experts?
You are exactly right that you need some in the tank to have additional bacteria growth. It's not uncommon for the nitrite to nitrate part of the cycle to be a few weeks behind the ammonia to nitrite part and even to be slow in completely growing out. It sound like you are coming along in fairly normal progress personally. The nitrite level is boarderline. I would rather see it around 1 ppm for the health of the fish. The nitrates are just fine, nothing at all to worry about there. I would suggest a series of small water changes to lower the nitrites a bit. Consider the type of fish you have and your current tank temperature and see if an increase of a few degrees in the tank temperature is possible, that might jump start the bacteria into completing the cycle. Also, lightly stir the surface of your gravel every few days to move bacteria colonies around a bit, that might encourage additional growth.





I am assuming you have an adequately sized power filter for the tank. Right?





MM
Reply:you said daily water changes? you shouldnt be changing your water daily that may be the reason for your problem. do you have fish in the tank or are you doing a fishless cycle? During the cycle there are a few stages.


1) amonia goes up


2) amonia keeps going up and nitrite rises


3) nitrite keeps riseing and amonia depletes


4) nitrate begins to rise and nitrite depletes


5) nitrate should then deplete


the bacteria is what breaks down these toxins so possibly by doing your daily water changes you are removing some of this bacteria needed to let the tank cycle.


Please give more info as to what size tank what fish are in there and anything else that you can think of.
Reply:Ok, do not worry about the nitrates if it is a freshwater tank. For the nitrites, I would get a product at a local petsmart, or petco that locks the nitrites making them non-toxic. Test your water again, and check to see if nitrites are zero, and nitrates if its saltwater. Then when they are zero, do a 20% water change, and you are set. If it goes back up, make sure to add the lock, and do the change sometime in that week
Reply:I know everyone has their own methods of cycling their tanks which work for them, in my experience if you just leave your tank alone and let it go through its cycle and possibly remove any carbon in your filters this may help eliminate all nitrites. And no you dont want to have any ammonia or nitrites in your tank, this should only happen during the initial cycling process. Nitrites at 2 are a little high keeping them under .4 is ideal and nitrates under 40 or 60 is good. So i would just try leaving the tank alone feeding minimally and removing carbon and see how that does for you in the next week to see if the nitrites lower.
Reply:Hi -





do you have any plants in your tank - floating and/or planted plants?





They'll help with the nitrate and nitrite levels - to keep them down. Anacharis is a good one for tanks. It will also oxygenate the water. I think it's one of the best.





Good Luck,





Ken

Staphylococcus bacteria in your nose?

How do we not get ill from that? Does the bacteria have to get into a cut, etc., in order to be dangerous to our health? Can the bacteria be spread from sneezing, picking (gross), etc.?

Staphylococcus bacteria in your nose?
Staphylococcus aureus, often referred to simply as "staph," are bacteria commonly carried on the skin or in the nose of healthy people. Approximately 25% to 30% of the population is colonized (when bacteria are present, but not causing an infection) in the nose with staph bacteria.





Sometimes, staph can cause an infection. Staph bacteria are one of the most common causes of skin infections in the United States. Most of these skin infections are minor (such as pimples and boils) and can be treated without antibiotics.





Staph bacteria also can cause serious infections (such as surgical wound infections, bloodstream infections, and pneumonia).





One area that is of concern is MRSA (methicillin resistant Staph aureus). While 25% to 30% of the population is colonized with staph, approximately 1% is colonized with MRSA.





Usually when staph is in your nose, you can be a carrier. Staph or MRSA infections in the community are usually manifested as skin infections, such as pimples and boils, and occur in otherwise healthy people.





MRSA is transmitted most frequently by direct skin-to-skin contact.





Most importantly, you can protect yourself from infections by practicing good hygiene; covering any open skin area such as abrasions or cuts with a clean dry bandage; avoiding sharing personal items such as towels or razors.
Reply:Yes it can spread by sneezing or having your finger in your nose and touching other surfaces. We don't get sick unless the bacteria spread from your nares to another part of your body.
Reply:If you are not ill you more then likely will not get MRSA. However, like my friend you can become a CARRIER for it due to having surgery after surgery, hospitalization after hospitalization. The bacteria can spread anyway a regular bacteria can spread.

dendrobium

What happens to bacteria that were used in a procedure that have been incubated for a longer period of time?

this bacteria was used for a Gram staining prodcedure. Before it was used, the bacteria was incubated for a long period of time. Would this alter the result in anyway? Does the bacteria cell walls get stronger or weaker with time?

What happens to bacteria that were used in a procedure that have been incubated for a longer period of time?
Unless you were constantly adding nutrients to your cell culture, (and unless you have some really expensive equipment, you were not), the bacteria would stop growing.





When that happens, the cell wall would become weaker.





The Gram stain uses Crystal violet dye which stains the thick peptidoglycan layer in the cell walls of Gram positive bacteria. If bacteria do not have this layer, they will not keep the crystal violet stain when washed with your decolorizer (usually acetone or alcohol). So the cells would only take up your counterstain (safranin, a red/pink dye). This would normally indicate that the bacteria are Gram negative.





Therefore if you have an old culture, the peptidoglycan of the cell wall would not hold the crystal violet dye. So no matter whether your bacteria are Gram positive or negative, you would only see pink bacteria.





So this would cause gram positive bacteria to appear gram negative.
Reply:This really depends on the type of culture and nutrient base used to colonize the bacteria. If the nutrient base runs out the microbes typically turn to one another for survival. In which case most will die as a result. If you there is enough nutrient base and environmental temperatures/pH is able to sustain microbial life you will have constant colonization.