Department of Life Sciences, Ben Gurion University of the Negev Beer-Sheva, 84105, Israel.
Ecol Evol. 2012 Oct;2(10):2521-6. doi: 10.1002/ece3.354. Epub 2012 Sep 1.
Bacteriocins are bacteriocidal toxins released by almost all bacteria. They are thought to have a narrow range of killing, but as bacteriocin-mediated interactions have been rarely studied at biologically relevant scales, whether this narrow range of action falls mostly within or mostly between coexisting species in natural communities is an open question with important ecological and evolutionary implications. In a previous study, we systematically sampled Xenorhabdus bacteria along a hillside and found evidence for genotypic variability and bacteriocin-mediated interactions within Xenorhabdus bovienii and X. koppenhoeferi colonies that were collected only a few meters apart. In contrast, colonies that were isolated from the same soil sample were always genetically similar and showed no inhibitions. Here, we conducted pairwise growth-inhibition assays within and between seven X. bovienii and five X. koppenhoeferi colonies that were isolated from different soil samples; all seven X. bovienii colonies and at least three of the X. koppenhoeferi have been distinguished as distinct genotypes based on coarse-grain genomic markers. We found signatures for both conspecific and heterospecific bacteriocin inhibitions in this natural community of Xenorhabdus bacteria, but intraspecific inhibitions were significantly more common than interspecific inhibitions. These results suggest that bacteriocins have a major role in intraspecific competition in nature, but also suggest that bacterocins are important in mediating interspecific interactions among coexisting species in natural communities.
细菌素是几乎所有细菌释放的杀菌毒素。它们被认为具有狭窄的杀伤范围，但由于细菌素介导的相互作用在生物学相关尺度上很少被研究，因此这种狭窄的作用范围主要发生在自然群落中共存的物种内还是物种间，是一个具有重要生态和进化意义的悬而未决的问题。在之前的一项研究中，我们沿着山坡系统地采样了 Xenorhabdus 细菌，发现了 Xenorhabdus bovienii 和 X. koppenhoeferi 菌落在相隔仅几米的地方存在基因型变异和细菌素介导的相互作用的证据。相比之下，从同一土壤样本中分离出的菌落总是具有相似的遗传特征，并且不存在抑制作用。在这里，我们在来自不同土壤样本的七个 Xenorhabdus bovienii 和五个 X. koppenhoeferi 菌落之间以及内部进行了两两生长抑制测定；根据粗粒基因组标记，所有七个 Xenorhabdus bovienii 菌落和至少三个 X. koppenhoeferi 菌落都被区分成不同的基因型。在 Xenorhabdus 细菌的这个自然群落中，我们发现了同种和异种细菌素抑制的特征，但种内抑制明显比种间抑制更为常见。这些结果表明，细菌素在自然界中种内竞争中起着重要作用，但也表明细菌素在介导自然群落中共存物种的种间相互作用方面很重要。
