Abstract：
Microbial extracellular polymeric substances (EPS) are an important component in sediment ecology. However, most research is highly skewed towards the northern hemisphere and in more permanent systems. This paper investigates EPS (i.e., carbohydrates and proteins) dynamics in arid Austral zone temporary pans sediments. Colorimetric methods and sequence-based metagenomics techniques were employed in a series of small temporary pan ecosystems characterised by alternating wet and dry hydroperiods. Microbial community patterns of distribution were evaluated between seasons (hot-wet and cool-dry) and across depths (and inferred inundation period) based on estimated elevation. Carbohydrates generally occurred in relatively higher proportions than proteins; the carbohydrate:protein ratio was 2.8:1 and 1.6:1 for the dry and wet season respectively, suggesting that EPS found in these systems was largely diatom produced. The wet- hydroperiods (Carbohydrate mean 102 μg g-1; Protein mean 65 μg g-1) supported more EPS production as compared to the dry- hydroperiods (Carbohydrate mean 73 μg g-1; Protein mean 26 μg g-1). A total of 15,042 Unique Amplicon Sequence Variants (ASVs) were allocated to 51 bacterial phyla and 1127 genera. The most abundant genera had commonality in high temperature tolerance, with Firmicutes, Actinobacteria and Proteobacteria in high abundances. Microbial communities were more distinct between seasons compared to within seasons which further suggested that the observed metagenome functions could be seasonally driven. This study\'s findings implied that there were high levels of denitrification by mostly nitric oxide reductase and nitrite reductase enzymes. EPS production was high in the hot-wet season as compared to relatively lower rates of nitrification in the cool-dry season by ammonia monooxygenases. Both EPS quantities and metagenome functions were highly associated with availability of water, with high rates being mainly associated with wet- hydroperiods compared to dry- hydroperiods. These data suggest that extended dry periods threaten microbially mediated processes in temporary wetlands, with implications to loss of biodiversity by desiccation.
摘要：
微生物胞外聚合物(EPS)是沉积物生态学的重要组成部分。然而,大多数研究高度偏向北半球和更永久的系统。本文研究了每股收益(即，碳水化合物和蛋白质）干旱的南方地区临时平底锅沉积物中的动态。比色法和基于序列的宏基因组学技术被用于一系列以干湿水文周期交替为特征的小型临时泛生态系统中。根据估计的海拔，评估了季节之间（热湿和冷干）和深度之间（以及推断的淹没期）的微生物群落分布模式。碳水化合物的比例通常高于蛋白质；干季和雨季的碳水化合物：蛋白质比例分别为2.8：1和1.6：1，这表明在这些系统中发现的EPS主要是硅藻产生的。与干水期相比，湿水期（碳水化合物平均为102μgg-1；蛋白质平均为65μgg-1）支持更多的EPS产生（碳水化合物平均为73μgg-1；蛋白质平均为26μgg-1）。总共15,042个独特扩增子序列变体(ASV)被分配到51个细菌门和1127个属。最丰富的属在耐高温方面具有共性，与Firmicutes，放线菌和变形菌丰度高。与季节内相比，季节之间的微生物群落更加不同，这进一步表明观察到的宏基因组功能可能是季节性驱动的。这项研究的发现暗示有高水平的反硝化作用主要通过一氧化氮还原酶和亚硝酸还原酶。与氨单加氧酶在凉爽干燥季节的硝化速率相对较低相比，在湿热季节的EPS产量很高。EPS数量和宏基因组功能都与水的可用性高度相关，与干水期相比，高速率主要与湿水期有关。这些数据表明，延长的干旱期威胁着临时湿地中微生物介导的过程，导致生物多样性因干燥而丧失。
