Temperature mediates biodiversity and metabolism of culturable lignocellulose-degrading consortia from intertidal wetlands

Coastal bacteria play an important role in the conversion of terrestrial organic carbon (TerrOC). However, their ecological patterns and drivers remains elusive. Here, 180 bacterial communities from 10 regions along the Chinese coastline, covering an 18 000 km transect between 18.27°N and 39.82°N, were cultured under three typical lignocellulosic substrates, hardwood (aspen), softwood (pine), and herbaceous (rice straw), respectively. All the consortia showed a broad spectrum of TerrOC utilization, and displayed degradation capacities comparable with those previously established though preliminary in situ lignocellulose enrichment. Moreover, following the metabolic theory of ecology, annual average temperature of the sites stimulated community metabolism, even though all were cultured at 30°C. Consortia enriched on aspen exhibited the highest temperature sensitivity. 16S rRNA gene amplicon and metatranscriptomic sequencing analyses revealed temperature-dependent latitudinal diversity gradients, displaying a trend that was opposite of the temperature-diversity positive relationship observed in terrestrial lignin-degrading microbes. The community composition shifted to adapt to rising environmental temperature. To enhance lignin degradation, aspen consortia from high annual average temperature employed metabolic generalists, which induced expression of dypB centered gene families for lignin depolymerization and versatile pathways for degradation of lignin derivates. This study reveals the intrinsic drivers for coastal cultured lignocellulose degrading bacterial communities from an ecological perspective and deepens our understanding of the metabolic mechanisms in coastal TerrOC conversion.