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Hey non-user here, don't know how the hell to work this site. Make sure you read item number 3 in the Phases section. There's some very unacademic statements being tossed around ("it's better to forget this"), thought you might want to fix that up. Love <3 Edit;another users: Omg exponential growth is really hard, all those doing biotech and bio stuff, dont give up........ love frank
— Preceding unsigned comment added by 98.228.92.241 ( talk) 04:08, 13 August 2012 (UTC)
The graph is certainly incorrect if "B" is supposed to look like exponential growth. Michael Hardy 22:49, 22 May 2004 (UTC)
It says:
This is contradictory! It cannot be growing at its maximum rate while it's growing exponentially. See exponential growth. While something is growing exponentially, its growth rate is always increasing; it's never at its maximum growth rate. I can't help suspecting this of being a case of thinking that "exponential growth" merely means extremely or surprisingly rapid growth. Besides, the description makes it sound like the growth rate is jointly proportional to the present size and the amount by which the size falls short of the carrying capacity. That would make it approximately exponential in its early phases, but nowhere near exponential when the growth rate is maximum. Michael Hardy 20:36, 15 Jul 2004 (UTC)
If the number of bacteria is increasing exponentially, and each bacterium is reproducing at maximum rate, then the rate of increase can be increasing exponentially, no problems at all. RobertStar20 22:38, 2 Nov 2004 (UTC)
I'm not entirely happy with the way this now reads; I'd like to see something more explicit about the mathematical model before such a phrase as "exponential growth" is used in a way that makes it appear to be meant literally. But maybe no one who knows this material has worked on this article. Michael Hardy 21:07, 8 Nov 2004 (UTC)
Time (h) Bacteria Count"
0 10
4 20
8 40
12 80
16 160
20 320
24 640
. .
. .
. .
This growth is modelled by the equation B = 10 x (2 ^ h/4), where B is the number of bacteria and h is the number of hours (x means multiply, ^ means exponent, / means divide)
So, the discussion is hopefully resolved with the accepted mathematical notion: Bacteria divide at a constant rate, hence their population grows exponentially.
I just tried to reread your page, and it referenced the exponential growth page, which says, "Examples of exponential growth Biology. Microorganisms in a culture dish will grow exponentially, at first, after the first microorganism appears (but then logistically until the available food is exhausted, when growth stops). "
If we assume the division of bacteria occurs at a constant rate (environment, other factors are constant) then the number of bacteria in any population will grow exponentially. It's the same for many types of populations, from rabbits to humans. If you assume that there is a constant steady growth rate, then the number in a population grows exponentially over time.
Or put another way, without external stressors, a population size will grow exponentially over time.
Have I missed something? This concept is as old as Malthus at least, who, I believe, pointed out that a population grows exponentially but resources tend to grow linearly and hence each population will tend to exhaust it's resources, inevitably.
I'd sure like to understand better if there is something I'm missing, or something I'm not explaining well. I thought the confusion was whether or not bacteria divide exponentially. They don't, or at least, as far as i understand, the rate of division is constant for given environmental factors. But because they divide, they double there number every time, which gives rise to an exponential function (base 2).
I appreciate you taking the time to respond to my comments. Please remember I am very new to Wikipedia, and if I break ediquette I don't mean to. Jess.
http://www.cellsalive.com/ecoli.htm "LOG PHASE: Once the metabolic machinery is running, they start multiplying exponentially, doubling in number every few minutes."
http://www.ugrad.math.ubc.ca/coursedoc/math100/notes/zoo/andromed.html
http://www.abc.net.au/science/experimentals/stories/s1168046.htm "Bacteria double in numbers about every 20 minutes - that's exponential growth!"
4 years on and the graph is still misleading... Since this graph represents the behaviour of many millions of bacteria, all transitions should be continuous (i.e. smooth) so the lag to log should curve to a straight line, the log to lag should curve to an approximately horizontal line, before curving down to the death phase line (i'm not sure what maths governs this phase). I'm no biologist, so my expertise is limited certainly, but Michael Hardy was correct to question the graph on the basis of its maths, atleast. Perhaps we could ask the user who created the graph image to edit it. Hai2410 ( talk) 17:17, 20 February 2010 (UTC)
First of all this is what I understand of it anyways. Once a bacterial population enter exponential phase as seen on the graph a theoretial maximum specific growth rate can be derived from from the graph.
(The difference between the theoretical and actual growth rate is determined by the concentration of limiting nutrient which is an essential growth factor necessary for bacterial growth that is consumed by bacteria before exhausting any other of the essential nutrients in the media.) The actual maximum specific growth rate or true maximum specific growth rate is determined in a chemostat. see http://mic.sgmjournals.org/cgi/reprint/151/10/3153 (for ref which states the reason they are growing approximately exponentially) They therefore could grow exponentially but they don't for these reasons.
Determining maxium specific growth rate is a two step calculation.
Step one: Determine the doubling time (generation time) the amount of time taken for the amount of cells in a population to double. (Also called doubling time) for the population. The time taken for the y value (bacterial cell number or turbidity of culture) to double. If the value doesn't increase extrapolate the line and read off your values.
Step two:
Derive maximum specific growth rate
maximum specific growth rate=Ln 2/doubling time
For the sake of the calculation, the fact that it is an approx value is close to the actual value is only going to make a small difference in the calculation of growth rate. (follow this methodology and repeat it a number of times to reduce your error). Bacteria have different maximum specific growth rates depending on the experimental conditions such as the media used if not stressed diverting the energy used for growth into non-growth processes into adaptation I think the only variable is the concentration of limiting nutrient which changes depending on the media used.
If you would like to determine the actual growth rate you need to establish a bacterial culture in a chemostat.
Alter the dilution rate of the chemostat such that the bacterial population (as measured by culture turbidity, or cell number cfu/ml) remains constant over time.
Oh yeah dilution rate = flow rate (the rate of addition of media to the chemostat) divided by the volume of the chemostat culture. also see paper maths explained better http://mic.sgmjournals.org/cgi/reprint/151/10/3153
Compare to values obained for batch culture and volia you have calculated your actual maximum specific growth rate and validated your result using two methods. The results agree (I've done it myself)
So exponential phase or is where a close approximation of exponential growth is used to calculate a close approximation of doubling time which is in turn used to derive a close approximation of maximum specific growth rate as obtained by a graph monitoring bacterial growth in batch culture is a method of determining growth.
A graph displaying exponential growth and does not look all that different from the one displayed in the figure depicting a bacterial population experiencing log growth occuring during log phase associated with this article. However it is not quite exactly strictly speaking true as true log growth cannot be derived because of the dependency on concentration of limiting nutrient in the media Lilypink ( talk) 18:03, 24 January 2008 (UTC)
Actually this is part of a much larger discussion about what happens in nature and what happens in culture; the question might be phrased: "What is acclimation and what is evolution?" It is a problem inherent in typological thinking. As a point of fact, bacteria are never (it seems) adapted to an environment in which every nutrient is present completely in excess. Instead, they have all sorts of throttles on their growth, which can be removed by various means. The 'deeper' the throttle, the more difficult to remove and the more difficult to reestablish. So there are all sorts of little things that a bacteria can do to adapt to slightly more rich environs for a short time, but over time it becomes further and further adapted to a regularly rich environment. Eventually it will start picking up mutations, some more routine and predictable than others (like cassette mechanisms), to more or less permanently alter its maximum doubling rate. The shortest term up and down regulation we probably never see in the lab, unless we produce microscale nutrient patches in a microfluidics device (see the work of F. Azam, J. Seymour, or R. Stocker). The medium scale is probably what we describe as lag phase, where the growth rate is less than we will see later in the culture. People who work on this know that max. growth rate is actually highly dependent not only on strain and media and temperature, but on inoculation size and observable population density. Anyway, you can create a system in which there is no limiting nutrient - every nutrient is in excess - and try to measure the growth rate, but this rate keeps changing as the organisms continue to adapt. Anyway, you do have periods of true log growth, with a fixed doubling time, to be sure. You just have to observe at the appropriate temporal and spatial scales. Bckirkup ( talk) 15:26, 25 January 2008 (UTC)
I think "Bacterial Growth Curve" should redirect to this page. It doesn't seem to exist as a page on its own, but it would make sense for it to point here. No? —Preceding unsigned comment added by 24.47.186.143 ( talk) 17:37, 2 April 2008 (UTC)
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Can anybody help how these Ro and Re fit in a bacterial growth formula? Thy SvenAERTS ( talk) 09:05, 19 July 2020 (UTC)
Myakubu has now added the following sentence three times:
it should be noted that rapid growths of bacteria in the bloodstream causes an exaggerated and destructive intravascular inflammatory response, which in turn leads to progressive circulatory collapse. [1]
I have reverted the addition twice for several reasons, the most important of which is that it is irrelevant to this article. The article is about the process by which bacteria grow and replicate. It is not about the effects of bacterial infections. It appears that Myakubu randomly googled the term "bacterial growth" and added a factoid from any random article containing the phrase to this article without concertn for its relevancy to the article. I have not reverted a third time, for fear of entering into a WP:3RR violation, so I bring the matter here for discussion. Myakubu, please explain why you feel that this sentence is relevant to this article. Other editors are, of course, free to weigh in. WikiDan61 ChatMe! ReadMe!! 20:35, 1 November 2022 (UTC)
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