Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109-1048, United States.
Mol Phylogenet Evol. 2011 Dec;61(3):834-43. doi: 10.1016/j.ympev.2011.08.006. Epub 2011 Aug 16.
Flashlight fishes (Beryciformes: Anomalopidae) harbor luminous symbiotic bacteria in subocular light organs and use the bacterial light for predator avoidance, feeding, and communication. Despite many attempts anomalopid symbionts have not been brought into laboratory culture, which has restricted progress in understanding their phylogenetic relationships with other luminous bacteria, identification of the genes of their luminescence system, as well as the nature of their symbiotic interactions with their fish hosts. To begin addressing these issues, we used culture-independent analysis of the bacteria symbiotic with the anomalopid fish, Anomalops katoptron, to characterize the phylogeny of the bacteria and to identify the genes of their luminescence system including those involved in the regulation of luminescence. Analysis of the 16S rRNA, atpA, gapA, gyrB, pyrH, recA, rpoA, and topA genes resolved the A. katoptron symbionts as a clade nested within and deeply divergent from other members of Vibrionaceae. The bacterial luminescence (lux) genes were identified as a contiguous set (luxCDABEG), as found for the lux operons of other luminous bacteria. Phylogenetic analysis based on the lux genes confirmed the housekeeping gene phylogenetic placement. Furthermore, genes flanking the lux operon in the A. katoptron symbionts differed from those flanking lux operons of other genera of luminous bacteria. We therefore propose the candidate name Candidatus Photodesmus (Greek: photo = light, desmus = servant) katoptron for the species of bacteria symbiotic with A. katoptron. Results of a preliminary genomic analysis for genes regulating luminescence in other bacteria identified only a Vibrio harveyi-type luxR gene. These results suggest that expression of the luminescence system might be continuous in P. katoptron.
发光鱼类（Beryciformes: Anomalopidae）在眼眶下的光器官中寄生发光共生细菌，并利用细菌光来躲避捕食者、觅食和交流。尽管人们多次尝试，但异常光鱼的共生菌仍未能在实验室中培养，这限制了人们对其与其他发光细菌的系统发育关系、发光系统基因的鉴定以及它们与鱼类宿主共生关系的本质的理解。为了解决这些问题，我们使用与异常光鱼 Anomalops katoptron 共生的细菌的非培养分析来描述细菌的系统发育，并鉴定其发光系统的基因，包括与发光调控相关的基因。16S rRNA、atpA、gapA、gyrB、pyrH、recA、rpoA 和 topA 基因的分析将 A. katoptron 共生菌解析为一个分支，嵌套在其他弧菌类成员内部，并与之有很深的分歧。细菌发光（lux）基因被鉴定为一组连续的基因（luxCDABEG），与其他发光细菌的 lux 操纵子相同。基于 lux 基因的系统发育分析证实了看家基因的系统发育位置。此外，A. katoptron 共生菌中 lux 操纵子侧翼的基因与其他发光细菌属 lux 操纵子侧翼的基因不同。因此，我们提议将与 A. katoptron 共生的细菌命名为 Photodesmus（希腊语：photo = light，desmus = servant）katoptron。对其他细菌中调节发光的基因进行的初步基因组分析结果仅鉴定出一个 Vibrio harveyi 型 luxR 基因。这些结果表明，在 P. katoptron 中，发光系统的表达可能是连续的。
