Cottrell M T, Wood D N, Yu L, Kirchman D L
College of Marine Studies, University of Delaware, Lewes, Delaware 19958, USA.
Appl Environ Microbiol. 2000 Mar;66(3):1195-201. doi: 10.1128/AEM.66.3.1195-1201.2000.
PCR primers were patterned after chitinase genes in four gamma-proteobacteria in the families Alteromonadaceae and Enterobacteriaceae (group I chitinases) and used to explore the occurrence and diversity of these chitinase genes in cultured and uncultured marine bacteria. The PCR results from 104 bacterial strains indicated that this type of chitinase gene occurs in two major groups of marine bacteria, alpha- and gamma-proteobacteria, but not the Cytophaga-Flavobacter group. Group I chitinase genes also occur in some viruses infecting arthropods. Phylogenetic analysis indicated that similar group I chitinase genes occur in taxonomically related bacteria. However, the overall phylogeny of chitinase genes did not correspond to the phylogeny of 16S rRNA genes, possibly due to lateral transfer of chitinase genes between groups of bacteria, but other mechanisms, such as gene duplication, cannot be ruled out. Clone libraries of chitinase gene fragments amplified from coastal Pacific Ocean and estuarine Delaware Bay bacterioplankton revealed similarities and differences between cultured and uncultured bacteria. We had hypothesized that cultured and uncultured chitin-degrading bacteria would be very different, but in fact, clones having nucleotide sequences identical to those of chitinase genes of cultured alpha-proteobacteria dominated both libraries. The other clones were similar but not identical to genes in cultured gamma-proteobacteria, including vibrios and alteromonads. Our results suggest that a closer examination of chitin degradation by alpha-proteobacteria will lead to a better understanding of chitin degradation in the ocean.
聚合酶链反应（PCR）引物是根据交替单胞菌科和肠杆菌科中四种γ-变形菌的几丁质酶基因设计的（第一类几丁质酶），并用于探索这些几丁质酶基因在培养的和未培养的海洋细菌中的存在情况和多样性。对104株细菌的PCR结果表明，这类几丁质酶基因存在于海洋细菌的两大主要类群——α-和γ-变形菌中，但在噬纤维菌-黄杆菌类群中不存在。第一类几丁质酶基因也存在于一些感染节肢动物的病毒中。系统发育分析表明，分类学上相关的细菌中存在相似的第一类几丁质酶基因。然而，几丁质酶基因的总体系统发育与16S rRNA基因的系统发育并不一致，这可能是由于几丁质酶基因在细菌类群之间的横向转移，但其他机制，如基因复制，也不能排除。从太平洋沿岸和特拉华湾河口浮游细菌中扩增得到的几丁质酶基因片段的克隆文库揭示了培养细菌和未培养细菌之间的异同。我们曾假设培养的和未培养的几丁质降解细菌会有很大不同，但实际上，具有与培养的α-变形菌几丁质酶基因核苷酸序列相同的克隆在两个文库中都占主导地位。其他克隆与培养的γ-变形菌中的基因相似但不完全相同，包括弧菌和交替单胞菌。我们的结果表明，更深入地研究α-变形菌的几丁质降解将有助于更好地理解海洋中的几丁质降解。
