联合与战斗：虚拟细菌之间的战争

[编者的话]

细菌的毒性（toxin production）、抗性（toxin resistance）是一种相生相克的关系，如果让同时具有毒性和抗性的几种不同细菌在一起相处，会发生什么呢，来自匈牙利的科学家在虚拟细菌中模拟了这一想法，研究人员发现让虚拟细菌相互玩一场复杂的石头剪刀布的游戏，细菌会令人惊讶地形成联盟。“这是崭新的结果”研究人员Jacqueline Fetherston这样评价到：“尽管这种情形目前只见于虚拟细菌，细菌家系之间联合起来进行战斗的情况很有可能在真实世界中同样发生着，这是一个可以验证的假说”

Virtual bacteria wargames catch virulence theory off guard

by Larry O'Hanlon，BioMedNet News

Pitting virtual bacteria against virtual bacteria ，Hungarian researchers have theorized that microbes can form surprising alliances while playing a high-stakes ，complex version of the game Rock ，Paper，Scissors. Applying what's known about how bacteria use toxins to compete with other bacterial strains ，researchers Gy ？rgy Szaból ，of the Research Institute for Technical Physics and Materials Science in Budapest and Tam ás Cz ár án of the Hungarian Academy of Sciences have simulated a battle among nine bacterial strains. As in the children's game in which rock always beats scissors and scissors can always top paper，bacterial strains in the simulation have properties that determine their competitive strength. Each strain has two of three characteristics：toxin production ，toxin resistance or vulnerability.

" （It）mimics the biochemical war among bacteria capable of producing two different bacteriocins（toxins），" writes Szab ól in this week's issue of Physical Review E，a sister journal to Physical Review Letters. The result of the simulated war was some unexpected situations where competing bacteria suddenly allied with each other to kill off other strains.

"That is new，" said researcher Jacqueline Fetherston of the University of Kentucky's College of Medicine ，commenting on the proposed bacterial alliances. Although it's only now seen in simulated bacteria，the idea of bacterial strains ganging up is something that could be looked for in the real-world ，she says. "It is at least a testable hypothesis."

In the most basic form，the theoretical war game played by bacteria involves three kinds of bacteria："Killers" which produce toxins ，"Resistant s" which resist the toxins of the Killers，and "Sensitives" which can be killed by the toxins. It might at first seem like the Killers would do best in this war. But as Resistants outnumber Killers ，who are wasting energy producing toxins ，the Sensitives - which produce neither toxins or resistance to them - can out-compete Resistants by spending the most energy on reproduction.

Szabó1 and Czár án added a new twist to the game by enabling their virtual bacteria to have up to two toxins and equivalent resistance factors. The result was nine strains of related bacteria with combinations of Killer （K ），Resistant（R ）and Sensitive（S ）traits ：KK ，KS ，KR ，SS，SR ，RR ，etc. The simulated bacteria were then allowed to fight. Among the more surprising results was that bacteria sometimes formed triad alliances with their worst enemies and wiped out the six other strains.

In one case KK，RR and SS strains ganged up on the others and won. When an RS invaded，it could out-do RRs，because it was using less energy to produce resistance. But it could not overthrow KK（since RS is sensitive to one toxin）and SS strains（because SS wastes no energy on defense or offense）。Just about any other strain invading the KK-RR-SS alliance faces a similar fate，say the researchers.