Biofilm Formation by Clostridium ljungdahlii Is Induced by Sodium Chloride Stress: Experimental Evaluation and Transcriptome Analysis

PLoS One. 2017 Jan 24;12(1):e0170406. doi: 10.1371/journal.pone.0170406. eCollection 2017.

Abstract

The acetogen Clostridium ljungdahlii is capable of syngas fermentation and microbial electrosynthesis. Biofilm formation could benefit both these applications, but was not yet reported for C. ljungdahlii. Biofilm formation does not occur under standard growth conditions, but attachment or aggregation could be induced by different stresses. The strongest biofilm formation was observed with the addition of sodium chloride. After 3 days of incubation, the biomass volume attached to a plastic surface was 20 times higher with than without the addition of 200 mM NaCl to the medium. The addition of NaCl also resulted in biofilm formation on glass, graphite and glassy carbon, the latter two being often used electrode materials for microbial electrosynthesis. Biofilms were composed of extracellular proteins, polysaccharides, as well as DNA, while pilus-like appendages were observed with, but not without, the addition of NaCl. A transcriptome analysis comparing planktonic (no NaCl) and biofilm (NaCl addition) cells showed that C. ljungdahlii coped with the salt stress by the upregulation of the general stress response, Na+ export and osmoprotectant accumulation. A potential role for poly-N-acetylglucosamines and D-alanine in biofilm formation was found. Flagellar motility was downregulated, while putative type IV pili biosynthesis genes were not expressed. Moreover, the gene expression analysis suggested the involvement of the transcriptional regulators LexA, Spo0A and CcpA in stress response and biofilm formation. This study showed that NaCl addition might be a valuable strategy to induce biofilm formation by C. ljungdahlii, which can improve the efficacy of syngas fermentation and microbial electrosynthesis applications.

Publication types

  • Comparative Study

MeSH terms

  • Biofilms / drug effects*
  • Biofilms / growth & development
  • Biomass
  • Carbon
  • Clostridium / drug effects*
  • Clostridium / genetics
  • Clostridium / physiology
  • Clostridium / ultrastructure
  • Culture Media
  • Culture Techniques / instrumentation
  • Fimbriae, Bacterial
  • Flagella
  • Gene Expression Profiling
  • Gene Expression Regulation, Bacterial
  • Glass
  • Graphite
  • Osmotic Pressure
  • RNA, Bacterial / genetics
  • RNA, Ribosomal / genetics
  • Sodium Chloride / pharmacology*
  • Spores, Bacterial
  • Stress, Physiological

Substances

  • Culture Media
  • RNA, Bacterial
  • RNA, Ribosomal
  • Sodium Chloride
  • Carbon
  • Graphite

Grants and funding

JP was funded by a postdoctoral grant of the Belgian American Educational Foundation (BAEF) and by the Special Research Fund (BOF) of the Ghent University. DRL was supported by an Office of Naval Research Grant (N000141310549). KR is supported by the European Research Council, starter grant ELECTROTALK. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.