Our pilot study to confirm our research methods has already found hundreds of species of bacteria and directed us to find out more about methane-producing microbes
Bacterial communities play a vital role in the degradation of pit latrine contents. But little is currently known about microbial diversity in latrine pits and how it contributes to the degradation of their contents. Our research is helping change this.
In 2010 we carried out a pilot study to confirm that our sampling methods and laboratory tests were working. From two latrines in Ifakara, Tanzania, and two in Vietnam’s Hanam province, we collected samples from different layers of their content. We analysed this successfully for different biochemical parameters (such as pH, temperature and Chemical Oxygen Demand). To help us understand which bacteria were present in these latrines, we also extracted DNA from each sample and sent it to the Wellcome Trust’s Sanger Institute in Cambridge (UK).
Discovering New Microbes
The Sanger Institute uses a special DNA sequencing technique (454 sequencing) which provides information about the composition of the microbial community and classification of bacterial species. Sequence data was analysed both at Glasgow University and at LSHTM using different protocols to identify the organisms present and their prevalence. The results of our pilot study indicated wide microbial diversity exists in pit latrines – both between countries and at different levels of pit depth. Many of these bacteria had never been cultured or identified before.
We found that the composition of latrine bacteria is different between Tanzania and Vietnam, with some groups of bacteria found more predominantly in one country. Our results showed:
- Highly diverse bacterial communities in latrines
- Bacterial communities clustering by geographic location and by individual latrine
- Large, broad-scale, differences in composition between Tanzania and Vietnam, with a broader diversity observed in Tanzanian pits
- Large numbers of previously uncultivated species.
This sequencing has been used for the first time to provide a powerful tool for investigating the microbial ecology of the latrines at an unprecedented level of detail. We are now extending this approach to samples taken from the cross-sectional and longitudinal studies. The insights we gain will be used for the future development of better designs and products for pit latrine users.
The Role of Methane Producers?
The latrine environment is largely anaerobic, so for successful breakdown of content the presence of methanogenic micro-organisms is required. These produce methane right at the end of the biochemical breakdown pathway. If they’re absent, the process will stall.
Our initial studies of microbial diversity didn’t include these organisms because special primers were needed to allow the sequencing to be conducted. These are now available, so we’re investigating the presence and distribution of methane producers within latrines. This will show us whether there’s a link between pits where contents break down efficiently and the presence of certain