Data_Sheet_3_Analysis of pit latrine microbiota reveals depth-related variation in composition, and key parameters and taxa associated with latrine fill-up rate.XLSX

Pit latrines are used by billions of people globally, often in developing countries where they provide a low-tech and low-cost sanitation method. However, health and social problems can arise from a lack of emptying or maintenance of these facilities. A better understanding of the biological and environmental parameters within pit latrines could inform attempts to enhance material decomposition rates, and therefore slow fill-up rate. In this study, we have performed a spatial analysis of 35 Tanzanian pit latrines to identify bacteria and environmental factors that are associated with faster or slower pit latrine fill-up rates. Using ordination of microbial community data, we observed a linear gradient in terms of beta diversity with increasing pit latrine sample depth, corresponding to a shift in microbial community structure from gut-associated families in the top layer to environmental- and wastewater-associated taxa at greater depths. We also investigated the bacteria and environmental parameters associated with fill-up rates, and identified pH, volatile solids, and volatile fatty acids as features strongly positively correlated with pit latrine fill-up rates, whereas phosphate was strongly negatively correlated with fill-up rate. A number of pit latrine microbiota taxa were also correlated with fill-up rates. Using a multivariate regression, we identified the Lactobacillaceae and Incertae_Sedis_XIII taxa as particularly strongly positively and negatively correlated with fill-up rate, respectively. This study therefore increases knowledge of the microbiota within pit latrines, and identifies potentially important bacteria and environmental variables associated with fill-up rates. These new insights may be useful for future studies investigating the decomposition process within pit latrines.

全球数十亿人使用坑式厕所（pit latrines），这类设施多分布于发展中国家，是一种低技术、低成本的卫生手段。然而，由于缺乏清掏或维护，这类设施可能引发健康与社会问题。若能更好地理解坑式厕所内的生物学与环境参数，或可为提升物料分解速率、进而减缓坑厕填充速度的尝试提供参考。本研究对35座坦桑尼亚的坑式厕所开展空间分析，旨在识别与坑厕填充速率快慢相关的细菌及环境因素。通过对微生物群落数据进行排序分析，我们观察到：随着坑厕采样深度增加，β多样性呈现线性梯度变化，微生物群落结构也随之转变——表层以肠道相关菌群为主，深层则转变为环境及废水相关类群。我们还探究了与填充速率相关的细菌及环境参数，发现pH值、挥发性固体与挥发性脂肪酸均与坑厕填充速率呈显著正相关，而磷酸盐则与填充速率呈显著负相关。此外，多种坑厕微生物类群也与填充速率存在关联。通过多元回归分析，我们鉴定出乳酸杆菌科（Lactobacillaceae）和Incertae_Sedis_XIII类群分别与填充速率呈极强的正相关与负相关。本研究因此增进了学界对坑式厕所内微生物群落的认知，并识别出与填充速率相关的潜在关键细菌与环境变量。这些新发现可为未来针对坑厕内分解过程的研究提供助力。