Kalenborn Saskia, Zühlke Daniela, Riedel Katharina, Amann Rudolf I, Harder Jens
Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany.
Department for Microbial Physiology and Molecular Biology, University of Greifswald, Felix-Hausdorff-Str. 8, D-17489 Greifswald, Germany.
FEMS Microbiol Ecol. 2024 Apr 10;100(5). doi: 10.1093/femsec/fiae045.
Arabinose and galactose are major, rapidly metabolized components of marine particulate and dissolved organic matter. In this study, we observed for the first time large microbiomes for the degradation of arabinogalactan and report a detailed investigation of arabinogalactan utilization by the flavobacterium Maribacter sp. MAR_2009_72. Cellular extracts hydrolysed arabinogalactan in vitro. Comparative proteomic analyses of cells grown on arabinogalactan, arabinose, galactose, and glucose revealed the expression of specific proteins in the presence of arabinogalactan, mainly glycoside hydrolases (GH). Extracellular glycan hydrolysis involved five alpha-l-arabinofuranosidases affiliating with glycoside hydrolase families 43 and 51, four unsaturated rhamnogalacturonylhydrolases (GH105) and a protein with a glycoside hydrolase family-like domain. We detected expression of three induced TonB-dependent SusC/D transporter systems, one SusC, and nine glycoside hydrolases with a predicted periplasmatic location. These are affiliated with the families GH3, GH10, GH29, GH31, GH67, GH78, and GH115. The genes are located outside of and within canonical polysaccharide utilization loci classified as specific for arabinogalactan, for galactose-containing glycans, and for arabinose-containing glycans. The breadth of enzymatic functions expressed in Maribacter sp. MAR_2009_72 as response to arabinogalactan from the terrestrial plant larch suggests that Flavobacteriia are main catalysts of the rapid turnover of arabinogalactans in the marine environment.
阿拉伯糖和半乳糖是海洋颗粒有机物和溶解有机物的主要成分，且能被快速代谢。在本研究中，我们首次观察到用于降解阿拉伯半乳聚糖的大型微生物群落，并详细报道了黄杆菌属Maribacter sp. MAR_2009_72对阿拉伯半乳聚糖的利用情况。细胞提取物在体外可水解阿拉伯半乳聚糖。对在阿拉伯半乳聚糖、阿拉伯糖、半乳糖和葡萄糖上生长的细胞进行的比较蛋白质组分析表明，在有阿拉伯半乳聚糖存在时会表达特定蛋白质，主要是糖苷水解酶（GH）。细胞外聚糖水解涉及5种属于糖苷水解酶家族43和51的α-L-阿拉伯呋喃糖苷酶、4种不饱和鼠李糖半乳糖醛酸水解酶（GH105）以及一种具有糖苷水解酶家族样结构域的蛋白质。我们检测到3种诱导型TonB依赖性SusC/D转运系统、1种SusC以及9种预测位于周质的糖苷水解酶的表达。这些酶属于GH3、GH10、GH29、GH31、GH67、GH78和GH115家族。这些基因位于被归类为特定于阿拉伯半乳聚糖、含半乳糖聚糖和含阿拉伯糖聚糖的典型多糖利用位点之外和之内。Maribacter sp. MAR_2009_72中表达的对来自陆生植物落叶松的阿拉伯半乳聚糖作出响应的酶促功能的广度表明，黄杆菌纲是海洋环境中阿拉伯半乳聚糖快速周转的主要催化剂。
