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2019:groups:g3:start [2018/12/28 17:36] – [References] andrade2019:groups:g3:start [2024/01/09 18:45] (current) – external edit 127.0.0.1
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 **Group 3** **Group 3**
  
-======= The worm is up: competition vs reproduction in a bacteria symbiont of a nematode =======+<html><font size=6 face="Arial">Bacteria fight dirty: competition vs reproduction in a bacteria symbiont of a nematode</font></html> 
  
 Wiki site of the practical exercise of the [[http://www.ictp-saifr.org/viii-southern-summer-school-on-mathematical-biology/|VIII Southern-Summer School on Mathematical Biology]]. Wiki site of the practical exercise of the [[http://www.ictp-saifr.org/viii-southern-summer-school-on-mathematical-biology/|VIII Southern-Summer School on Mathematical Biology]].
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 Symbiosis can be defined as "an interaction (positive, negative, or neutral) in which two species exist in intimate physical association for most or all of their lifetimes and are physiologically dependent on each other" [1]. This is the interaction between the bacteria //Xenorhabdus bovienii// and its host, the nematode //Steinernema affine//, on which it depends to colonize insects [2]. They infect the insect (caterpillars, for instance), get separated, and then both contribute to kill it. Once dead, the insect provides resources that allow reproduction of both species. When these resources are depleted, the bacteria and the nematode reunite and emerge from the insect. Symbiosis can be defined as "an interaction (positive, negative, or neutral) in which two species exist in intimate physical association for most or all of their lifetimes and are physiologically dependent on each other" [1]. This is the interaction between the bacteria //Xenorhabdus bovienii// and its host, the nematode //Steinernema affine//, on which it depends to colonize insects [2]. They infect the insect (caterpillars, for instance), get separated, and then both contribute to kill it. Once dead, the insect provides resources that allow reproduction of both species. When these resources are depleted, the bacteria and the nematode reunite and emerge from the insect.
  
-//Xenorhabdus// is able to produce a compound (bacteriocin) that inhibits bacteria from different strains inside the insect. Inhibiting strains of the bacteria show a clear advantage over non-inhibiting ones when they reproduce together inside the insect. However, non-inhibiting strains of //Xenorhabdus// are observed isolately (but not together with  inhibiting strains?). So how can both types persist in nature? That is the question that the authors, and perhaps yourselves, try to answer. +//Xenorhabdus// is able to produce a compound (bacteriocin) that inhibits bacteria from different strains inside the insect. Inhibiting strains of the bacteria show a clear advantage over non-inhibiting ones when they reproduce together inside the insect. However, non-inhibiting strains of //Xenorhabdus// are observed isolately, but generally not together with  inhibiting strains. So how can both types persist in nature? That is the question that the authors of [2], and perhaps yourselves, try to answer. 
  
 They hypothesize that there may be a reproductive cost for the bacteria associated with inhibiting other strains, and experimentally test it. Their results suggest that, indeed, on a non-competitive environment, non-inhibiting strains of //Xenorhabdus// are able to kill and reproduce faster than inhibiting ones. They hypothesize that there may be a reproductive cost for the bacteria associated with inhibiting other strains, and experimentally test it. Their results suggest that, indeed, on a non-competitive environment, non-inhibiting strains of //Xenorhabdus// are able to kill and reproduce faster than inhibiting ones.
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 <WRAP clear></WRAP> <WRAP clear></WRAP>
  
-<WRAP third column right> Figure: a) Nematode (//Steinernema affine//). b) Bacteria (//Xenorhabdus bovienii//). c) Caterpillar (//Malacosoma americanum//). Source: [2]</WRAP>+<WRAP third column right> **Figure**: Top - Nematode (//Steinernema affine//). Middle - Bacteria (//Xenorhabdus bovienii//). Bottom - Caterpillar (//Malacosoma americanum//). Source: [2]</WRAP>
  
 <WRAP clear></WRAP> <WRAP clear></WRAP>
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 ===== Questions & Suggestions ===== ===== Questions & Suggestions =====
  
-  * Nematode and bacteria cannot survive (or, at least, cannot reproduce) without each other - what happens to your model if one or the other is extinguished? 
   * Does your model allow some kind of coexistence between inhibiting and non-inhibiting bacteria?   * Does your model allow some kind of coexistence between inhibiting and non-inhibiting bacteria?
   * Can the dynamics of the insect host drastically change your conclusions?   * Can the dynamics of the insect host drastically change your conclusions?
2019/groups/g3/start.1546018570.txt.gz · Last modified: 2024/01/09 18:45 (external edit)