Effects of predation by protists on prokaryotic community function, structure, and diversity in anaerobic granular sludge

Yuga Hirakata, Mamoru Oshiki, Kyohei Kuroda, Masashi Hatamoto, Kengo Kubota, Takashi Yamaguchi, Hideki Harada, Nobuo Araki

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Predation by protists is top-down pressure that regulates prokaryotic abundance, community function, structure, and diversity in natural and artificial ecosystems. Although the effects of predation by protists have been studied in aerobic ecosystems, they are poorly understood in anoxic environments. We herein studied the influence of predation by Metopus and Caenomorpha ciliates—ciliates frequently found in anoxic ecosystems—on prokaryotic community function, structure, and diversity. Metopus and Caenomorpha ciliates were cocultivated with prokaryotic assemblages (i.e., anaerobic granular sludge) in an up-flow anaerobic sludge blanket (UASB) reactor for 171 d. Predation by these ciliates increased the methanogenic activities of granular sludge, which constituted 155% of those found in a UASB reactor without the ciliates (i.e., control reactor). Sequencing of 16S rRNA gene amplicons using Illumina MiSeq revealed that the prokaryotic community in the UASB reactor with the ciliates was more diverse than that in the control reactor; 2,885–3,190 and 2,387–2,426 operational taxonomic units (>97% sequence similarities), respectively. The effects of predation by protists in anaerobic engineered systems have mostly been overlooked, and our results show that the influence of predation by protists needs to be examined and considered in the future for a better understanding of prokaryotic community structure and function.

Original languageEnglish
Pages (from-to)279-287
Number of pages9
JournalMicrobes and environments
Volume31
Issue number3
DOIs
Publication statusPublished - 2016

Keywords

  • Anaerobic granular sludge
  • Anaerobic protozoa
  • Up-flow anaerobic sludge blanket (UASB) reactor

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Soil Science
  • Plant Science

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