Departamento de Genética, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, SP, Brazil.
Genet Mol Biol. 2012 Jan;35(1):142-8. doi: 10.1590/s1415-47572012005000017. Epub 2012 Feb 3.
The genus Methylobacterium comprises pink-pigmented facultative methylotrophic (PPFM) bacteria, known to be an important plant-associated bacterial group. Species of this group, described as plant-nodulating, have the dual capacity of producing cytokinin and enzymes, such as pectinase and cellulase, involved in systemic resistance induction and nitrogen fixation under specific plant environmental conditions. The aim hereby was to evaluate the phylogenetic distribution of Methylobacterium spp. isolates from different host plants. Thus, a comparative analysis between sequences from structural (16S rRNA) and functional mxaF (which codifies for a subunit of the enzyme methanol dehydrogenase) ubiquitous genes, was undertaken. Notably, some Methylobacterium spp. isolates are generalists through colonizing more than one host plant, whereas others are exclusively found in certain specific plant-species. Congruency between phylogeny and specific host inhabitance was higher in the mxaF gene than in the 16S rRNA, a possible indication of function-based selection in this niche. Therefore, in a first stage, plant colonization by Methylobacterium spp. could represent generalist behavior, possibly related to microbial competition and adaptation to a plant environment. Otherwise, niche-specific colonization is apparently impelled by the host plant.
甲基杆菌属包括粉红着色兼性甲基营养型（PPFM）细菌，已知是一种重要的植物相关细菌群体。该群体中的物种被描述为植物结瘤，具有双重能力，既能产生细胞分裂素，又能产生果胶酶和纤维素酶等酶，参与系统抗性诱导和在特定植物环境条件下固氮。本研究旨在评估来自不同宿主植物的甲基杆菌属分离株的系统发育分布。因此，对结构（16S rRNA）和功能 mxaF（编码甲醇脱氢酶的亚基）普遍基因的序列进行了比较分析。值得注意的是，一些甲基杆菌属分离株通过定植一种以上的宿主植物成为多宿主植物的专家，而其他分离株则仅存在于某些特定的植物物种中。mxaF 基因的系统发育与特定宿主栖息之间的一致性高于 16S rRNA，这可能表明在这个生态位中存在基于功能的选择。因此，在第一阶段，甲基杆菌属对植物的定殖可能代表了一般的行为，可能与微生物竞争和适应植物环境有关。否则，特定于生态位的定殖显然是由宿主植物驱动的。
