Table_1_Analysis of pit latrine microbiota reveals depth-related variation in composition, and key parameters and taxa associated with latrine fill-up rate.DOCX

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.

全球数十亿人使用粪坑式厕所（pit latrines），这类设施多见于发展中国家，是一种低技术、低成本的卫生解决方案。然而，缺乏清掏与维护的粪坑式厕所可能引发各类健康与社会问题。若能更深入地解析粪坑内的生物学与环境参数，或可为提升物料分解速率、延缓粪坑填装周期的相关尝试提供理论参考。本研究对35座坦桑尼亚境内的粪坑式厕所开展空间分析，旨在识别与粪坑填装速率快慢相关的细菌及环境因子。通过对微生物群落数据的排序分析，我们观察到β多样性（beta diversity）随粪坑样本深度增加呈现线性梯度变化，对应微生物群落结构从表层的肠道相关菌群科，逐步转变为深层的环境及污水相关类群。此外，我们还探究了与填装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与粪坑填装速率呈显著正相关，而磷酸盐则与填装速率呈显著负相关。同时，部分粪坑微生物类群也与填装速率存在关联。通过多元回归分析，我们确定乳杆菌科（Lactobacillaceae）与分类地位未定类群XIII（Incertae_Sedis_XIII）分别与填装速率呈极强的正相关与负相关。本研究增进了学界对粪坑式厕所微生物组的认知，并识别出与填装速率相关的潜在关键细菌与环境变量。这些新的研究发现可为未来针对粪坑内分解过程的相关研究提供借鉴。