Fitness Impact of Obligate Intranuclear Bacterial Symbionts Depends on Host Growth Phase.
Fitness Impact of Obligate Intranuclear Bacterial Symbionts Depends on Host Growth Phase.
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DOI：
10.3389/fmicb.2016.02084
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发表时间：
2016
影响因子：
5.2
通讯作者：
Schrallhammer M
中科院分区：
文献类型：
--
作者：
Bella C;Koehler L;Grosser K;Berendonk TU;Petroni G;Schrallhammer M
根据教科书的定义，寄生虫会降低寄主的适合度，而互助者则会提供好处。但生物和非生物因素会影响共生相互作用，因此在某些情况下，寄生虫可以提供好处，互助者可以伤害它们的宿主。在这里，我们讨论了哪些内在生物因素形成了共生关系，并对专性核内细菌Holospora caryophila(甲蛋白细菌；立克次门)与其单细胞真核宿主草履虫(Alveolata；纤毛目)之间相互作用的结果起关键作用。通过对几株嗜麦芽窄食单胞菌的生长测定，确定了其毒力，即对寄主分裂和细胞数量的负适合度效应。比较了感染嗜麦性嗜血杆菌和不含共生菌的遗传相同品系的表现。下列因素被认为可能影响相互作用的结果：(1)宿主菌株，(2)寄生虫菌株，和(3)宿主的生长阶段。所有这三个因素都显示出对共生的强烈影响。在嗜甲虫的存在下，草履虫在生长稳定期的密度降低。相反，对于几种寄主×寄生虫组合，在指数期观察到细菌的积极作用，从而提高了感染青霉病原虫的生长速度。此外，所测试的内共生菌对不同双金黄色葡萄球菌品系的适合度影响不仅取决于所涉及的两个菌株中的一个，而且对于特定的组合是不同的。根据当前寄主生长阶段的不同，嗜卡螺旋体的存在对青霉可能有害，也可能有利。因此，在所测试的实验条件下，共生体可以在相同的寄主种群内，在不超过6天的时间跨度内，从提供收益切换到开发寄主资源。
According to text book definition, parasites reduce the fitness of their hosts whereas mutualists provide benefits. But biotic and abiotic factors influence symbiotic interactions, thus under certain circumstances parasites can provide benefits and mutualists can harm their host. Here we addressed the question which intrinsic biotic factors shape a symbiosis and are crucial for the outcome of the interaction between the obligate intranuclear bacterium Holospora caryophila (Alphaproteobacteria; Rickettsiales) and its unicellular eukaryotic host Paramecium biaurelia (Alveolata; Ciliophora). The virulence of H. caryophila, i.e., the negative fitness effect on host division and cell number, was determined by growth assays of several P. biaurelia strains. The performances of genetically identical lines either infected with H. caryophila or symbiont-free were compared. Following factors were considered as potentially influencing the outcome of the interaction: (1) host strain, (2) parasite strain, and (3) growth phases of the host. All three factors revealed a strong effect on the symbiosis. In presence of H. caryophila, the Paramecium density in the stationary growth phase decreased. Conversely, a positive effect of the bacteria during the exponential phase was observed for several host × parasite combinations resulting in an increased growth rate of infected P. biaurelia. Furthermore, the fitness impact of the tested endosymbionts on different P. biaurelia lines was not only dependent on one of the two involved strains but distinct for the specific combination. Depending on the current host growth phase, the presence of H. caryophila can be harmful or advantageous for P. biaurelia. Thus, under the tested experimental conditions, the symbionts can switch from the provision of benefits to the exploitation of host resources within the same host population and a time-span of less than 6 days.
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DOI：
10.1007/978-3-540-92677-1_8
发表时间：
2009-01-01
期刊：
ENDOSYMBIONTS IN PARAMECIUM
影响因子：
--
作者：
Fujishima, Masahiro
通讯作者：
Fujishima, Masahiro
影响因子：
3.9
作者：
Amiri, H;Karlberg, O;Andersson, SGE
通讯作者：
Andersson, SGE
影响因子：
3.6
作者：
Boscaro, Vittorio;Fokin, Sergei I.;Petroni, Giulio
通讯作者：
Petroni, Giulio
影响因子：
2.9
作者：
Krenek, Sascha;Berendonk, Thomas U.;Petzoldt, Thomas
通讯作者：
Petzoldt, Thomas
影响因子：
3.4
作者：
Lambrechts, Louis;Chevillon, Christine;Scott, Thomas W.
通讯作者：
Scott, Thomas W.