Pedobacter hainanensis sp. nov., Isolated from Seaside Soil

Bacterial diversity and community along the succession of biological soil crusts in the Gurbantunggut Desert, Northern China

Biological soil crusts (BSCs) are common and play critical roles in semi-arid and arid ecosystems. Bacteria, as an important community in BSCs, play critical roles in biochemical processes. However, how bacterial diversity and community change in different successional stages of BSCs is still unknown. We used 454 pyrosequencing of 16S rRNA to investigate the bacterial composition and community, and the relationships between bacterial composition and environmental factors were also explored. In different successional stages of BSCs, the number of bacteria operational taxonomic units (OTUs) detected in each sample ranged from 2572 to 3157. Proteobacteria, Cyanobacteria, Bacteroidetes were dominant in BSCs, followed by Firmicutes, Acidobacteria, and Actinobacteria. At the successional stages of BSCs, bacterial communities, OTU composition and their relative abundance notably differentiated, and Cyanobacteria, especially Microcoleus vaginatus, dominated algal crust and lichen crust, and were the main C-fixing bacteria in BSCs. Proteobacteria and Bacteroidetes increased with the development of BSCs. OTUs related to Planomicrobium Chinese, Desulfobulbus sp., Desulfomicrobium sp., Arthrobacter sp., and Ahhaerbacter sp. showed higher relative abundance in bare sand than other successional stages of BSCs, while relative abundance of Sphingomonas sp. Niastella sp., Pedobacter, Candidatus solobacter, and Streptophyta increased with the development of BSCs. In successional stages of BSCs, bacterial OTUs composition demonstrated strong correlations with soil nutrients, soil salts, and soil enzymes. Additionally, variation of bacterial composition led to different ecological function. In bare sand, some species were related with mineral metabolism or promoting plant growth, and in algal crust and lichen crust, C-fixing bacteria increased and accumulated C to the desert soil. In later developed stage of BSCs, bacteria related with decomposition of organic matter, such as Sphingomonas sp. Niastella sp., Pedobacter, and Candidatus solobacter increased. Therefore, bacterial community composition and their key ecological roles shifted to the development of BSCs.

Electrospray ionization mass spectrometric analysis of κ-carrageenan oligosaccharides obtained by degradation with κ-carrageenase from Pedobacter hainanensis

κ-Carrageenan was degraded with a novel κ-carrageenase isolated from Pedobacter hainanensis, which was first isolated from seaside soil under the stacks of red algae in Hainan province of China. The κ-carrageenase was detected with a molecular weight of ∼55 kDa estimated from SDS-PAGE and yielded enzymatic activity of 700.53 units/mg of protein under the conditions of pH 7.0 and 40 °C. Analysis of the degradation products by TLC and HPLC indicated that the enzyme degraded κ-carrageenan to sulfated oligosaccharides with even-numbered degree of polymerization, of which the tetrasaccharide was the major product. All the degradation components during different time courses were analyzed by ESI-MS, and their structures were assigned. Structural analysis by CID MS/MS revealed that each carrageenan oligosaccharide was composed of An-G4S-type neocarrabiose units, which consisted of a 3,6-anhydro-α-d-galactose (An) residue in the nonreducing end and a β-d-galactose-4-sulfate (G4S) residue in the reducing end. These results demonstrated that the κ-carrageenase cleaved κ-carrageenan at the internal β-1,4 linkage of κ-carrageenan. This enzymatic degradation offers an alternative approach to prepare κ-carrageenan oligosaccharides, which could be used as a powerful tool for further study on biological activity-structure relationship and thorough industrial exploitation of κ-carrageenan.