Microbial community responses of an anaerobic enrichment to temperature shocks

Anaerobic digestion (AD) accomplishes degradation of complex organics in wastewater to methane and CO2 mediated by ecological cooperation of microorganisms with different metabolic functions. Previous studies have reported that temperature fluctuation could lead to AD process instability and failure, perhaps through disruption of microbial cooperation. Nevertheless, understanding of how AD microbiota respond to temperature shock is poor. Specifically, we have yet to identify organisms vulnerable to heat shock or responsible for recovering post-shock AD activity. To systematically address these questions, a mesophilic benzoate-degrading methanogenic enrichment was exposed to different levels of temperature perturbation from 45°C to 70°C for 5 or 15 min. Perturbations over this temperature gradient revealed three types of post-shock methane production profiles: no inhibition (45 and 50°C), initial inhibition with gradual recovery (55 and 60°C), and complete inhibition (70°C). These responses were also reflected in the RNA- and DNA- based 16S rRNA gene analysis of the microbial community. The primary benzoate-degrading syntroph (Syntrophus-related population) was highly affected by heat shock temperature, and its abundance was crucial to the restoration of benzoate degradation after the perturbation. In contrast, two major methanogen populations were relatively stable regardless whether methane production was inhibited. Other bacteria showed different response patterns, indicating distinct physiological and ecological traits. For example, a Firmicutes-related population rose to >50% abundance post shock, perhaps surviving through spore formation and thriving on detritus degradation. Members of “Ca. Cloacimonetes”, Spirochaetes, Bacteroidetes and Thermotogae were also stimulated while Desulfovibrio and another Spirochaetes member was inhibited. Though the exact roles of these minor microbial populations are unknown, their ubiquity across AD suggests that they are functionally important. Overall, temperature perturbation provided ecological characterization of core microbial populations in AD and can further generate knowledge on how to deal with unexpected heat shock, a common accident, thus improve the stability and performance of AD processes.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Environmental Engineering in Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Mei, Ran

Contributors dc:contributor

• Liu, Wen-Tso

• microbial community
• responses
• temperature shocks

Statement dc:rights

• Copyright 2015 Ran Mei

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/88243

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/88243