Castelli Michele, Gammuto Leandro, Podushkina Diona, Vecchi Matteo, Altiero Tiziana, Clementi Emanuela, Guidetti Roberto, Rebecchi Lorena, Sassera Davide
Department of Biology and Biotechnology, University of Pavia, Pavia, Italy.
Dipartimento di Scienze Della Vita, Università degli Studi di Modena e Reggio Emilia, Modena, Italy.
Environ Microbiol. 2025 Jan;27(1):e70028. doi: 10.1111/1462-2920.70028.
The Hepatincolaceae (Alphaproteobacteria) are a group of bacteria that inhabit the gut of arthropods and other ecdysozoans, associating extracellularly with microvilli. Previous phylogenetic studies, primarily single-gene analyses, suggested their relationship to the Holosporales, which includes intracellular bacteria in protist hosts. However, the genomics of Hepatincolaceae is still in its early stages. In this study, the number of available Hepatincolaceae genomes was increased to examine their evolutionary and functional characteristics. It was found that the previous phylogenetic grouping with Holosporales was incorrect due to sequence compositional biases and that Hepatincolaceae form an independent branch within the Hepatincolaceae. This led to a reinterpretation of their features, proposing a new evolutionary scenario that involves an independent adaptation to host association compared to the Holosporales, with distinct specificities. The Hepatincolaceae exhibit greater nutritional flexibility, utilising various molecules available in the host gut and thriving in anaerobic conditions. However, they have a less complex mechanism for modulating host interactions, which are likely less direct than those of intracellular bacteria. In addition, representatives of Hepatincolaceae show several lineage-specific traits related to differences in host species and life conditions.
肝柄菌科（α-变形菌纲）是一类栖息于节肢动物和其他蜕皮动物肠道内、与微绒毛细胞外相关联的细菌。先前的系统发育研究，主要是单基因分析，表明它们与全孢菌目有关，全孢菌目包括原生生物宿主内的细胞内细菌。然而，肝柄菌科的基因组学仍处于早期阶段。在本研究中，增加了可用的肝柄菌科基因组数量，以研究它们的进化和功能特征。研究发现，由于序列组成偏差，先前与全孢菌目进行的系统发育分组是不正确的，并且肝柄菌科在肝柄菌科内形成一个独立的分支。这导致了对它们特征的重新解释，提出了一种新的进化情景，即与全孢菌目相比，肝柄菌科涉及对宿主关联的独立适应，具有不同的特异性。肝柄菌科表现出更大的营养灵活性，利用宿主肠道中可用的各种分子，并在厌氧条件下茁壮成长。然而，它们调节宿主相互作用的机制不太复杂，可能比细胞内细菌的机制更不直接。此外，肝柄菌科的代表表现出一些与宿主物种和生活条件差异相关的谱系特异性特征。
