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How does bacteria live in dormancy

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Posted at 2013-9-20 04:01:23 | All floors |Read mode
Dormancy is a universal strategy for organisms to survive extreme enviromental conditions. It was repoted that bacteria preserved in Antactica ice for as long as 8 million years and resuscitated. Besides the metabolic network suspended during dormancy, the most incredible feature of dormant organism is self-mainteance. It is commonly accepted that organisms function as  system with negentropy by utilizing external energy to sustain and proliferation. Though energy consumption was minimized, the tendency of collapse persists during dormancy period. The question is, since the energy input is unavailable, how dormant organism keep intrinsic order from broken down. If the energy preserved before dormancy is only resource, can we build a model to calculate the limitation of certain organism?

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Posted at 2013-9-20 04:44:31 | All floors
Sounds interesting. Did anyone first quantified the "tendency of collapse" for a non-equilibrium system?
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 Author| Posted at 2013-9-20 07:42:13 | All floors
I'm not quite familiar to non-equilibrium dynamics.  Tendency of collapse in dormancy, I suppose, could be defined more specifically as the frequency of DNA  damage, if we assume all the other components such as proteins could be synthesis de novo.There are reports that DNA repair is preferential during resuscitation from dromancy.

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Posted at 2013-9-21 03:13:38 | All floors
Interesting question!
If I'm asked about this issue, I'd like to consider the following possible explainations (or in other words, the possible directions I would like to have a try):

1)If we consider this whole organism as a whole network, it could be devided into several functional modules. Each module acts as a sub-network and  communications with other sub-networks to fulfill the task of living. If we could do the experiments, perhaps we could measure the temperature and important elements that participate in the reactions of the dormance bacterias, and compare the data with the normal bacterias. Thus a possible model will be formed: the changed elements imply the changed modules (sub-networks), and we could study how the sub-networks' changes affect the whole network, through the aspect of dynamics.


2)We could also view the organism as a whole network, and consider following steps:
1、which parameters/nodes would affect the speed of the whole function, in other words, the period of the whole oscillating system?

2、What's the relationship between the temperature and the parameters/nodes we picked from the first step?( This step would require some experiments to test the reaction speed and the amount of certain chemical substances.

Jingyi

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Posted at 2013-9-21 07:58:11 | All floors
very interesting idea~

I think the most intriguing question in the dormancy is the ability of maintaining the highly-organized state. Based on Prigogine's theory, the maintenance of a dissipative structure requires energy. My naive idea is that in the normal state the organism dissipates energy not only to maintain their highly-organized state but also to amplify itself. As for the dormancy state, the energy cost is only used to the first part. Another idea may be relevant is that dormancy usually occurs in a lower temperature comparing to the temperature that the organism lives (such as frogs and snakes), which according to the themodynamics, will decrease the molecular Brown motions. It may also contribute to the ability of maintaining the highly-organized state.

As for the definition of 'tendency of collapse', my idea is that it's beyond the DNA damage. It should be a critical point, which is relevant to the state of the cell. When the state of the cell is beyond the critical point, the cell can on longer maintain the dormancy state but tend to death. So the tendency of collapse I think should include the concentrations and state of the main proteins in a cell (especially the cytoskeletal proteins for its organization usually reflects the state of the cell like apoptosis and necrosis).

Yan Jiawei

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 Author| Posted at 2013-9-21 13:00:30 | All floors
My experiment result suggest that there are three major "modules" involved in bacterial dormancy, membrane, ribosome and choromosome, and complex interactions among such modules. It is quite reasonable that I was wondering the possibilities to modeling dormancy process. My experience in modeling is scarce, so I suppose start with energy might be feasible to ignore detailed cellular network.

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Posted at 2013-9-21 14:49:38 | All floors
I like the idea that we could control the temperature during the dormancy which might be a important factor.  But I don't think considering the whole organism as a network will work in this particular question.  Flux Balance Analysis might work better, but I'm not sure.

I agree that the tendency of collapse is physical limitation, but I don't think it could be defined as a critical point.  I'm wondering if any experiment has been done, but I intuitionally guess the probability of survival is an exponential decline curve.  However, It's difficult to control the experimental condition to get rid of other influences during the survival test.
Working makes you tired; thinking drives you crazy!

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 Author| Posted at 2013-9-24 06:47:40 | All floors
Experiments of freeze-dried bacteria survival rate have been performing for over 30 years. After the initial imediate death about 50%, death of frozen bacteria is very slow, 10 percent of total alive after 3 decades.

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Posted at 2013-9-24 07:11:09 | All floors
Fleo Posted at 2013-9-24 06:47
Experiments of freeze-dried bacteria survival rate have been performing for over 30 years. After the ...

so for the bacteria who diy mediately and the ones that survive long, what's their difference in expression profile before the cooling? Or is the death stochastic?
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Posted at 2013-9-24 13:56:25 | All floors
Last edited by FishHead In 2013-9-24 14:56 Editor

I wonder whether the bacteria can be trained to adapt extreme environment. For example, if we put the bacteria very closely to
the dead state, and then pull it back before it is really dead. By doing this several times, can the ''weak'' bacteria becomes ''strong''?

And if this training can be realized in the lab (or maybe someone has already done it), comparing the data before and after training  may be more reliable, because individual differences are eliminated.

  

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 Author| Posted at 2013-9-25 08:16:05 | All floors
zhiyuanli Posted at 2013-9-24 07:11
so for the bacteria who diy mediately and the ones that survive long, what's their difference in e ...

It is the question. Peresisters, an active bacteria dormancy research field, is about a tiny minority non-growing bacteria which are insensitive to antibiotics .The underlying mechanism is obscure, and it is believed to be stochastically forming dormant individuals.
The intrinsic diversity in bacteria having the same genetic background is another interesting problem.

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Posted at 2013-9-26 08:49:31 | All floors
Why not try to compare dormancy to cell age? Like erythrocyte having 120 days, but leukocyte only a few days?
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