Effects of Antimicrobial Peptides on Methanogenic Archaea

Abstract

cAs members of the indigenous human microbiota found on several mucosal tissues, Methanobrevibacter smithii and Methanosphaera stadtmanae are exposed to the effects of antimicrobial peptides (AMPs) secreted by these epithelia. Although antimicrobial and molecular effects of AMPs on bacteria are well described, data for archaea are not available yet. Besides, it is not clear whether AMPs affect them as the archaeal cell envelope differs profoundly in terms of chemical composition and structure from that of bacteria. The effects of different synthetic AMPs on growth of M. smithii, M. stadtmanae, and Methanosarcina mazei were tested using a microtiter plate assay adapted to their anaerobic growth requirements. All three tested methanoarchaea were highly sensitive against derivatives of human cathelicidin, of porcine lysin, and a synthetic antilipopolysaccharide peptide (Lpep); however, sensitivities differed markedly among the methanoarchaeal strains. The potent AMP concentrations affecting growth were below 10 M, whereas growth of Escherichia coli WBB01 was not affected at peptide concentrations up to 10 M under the same anaerobic growth conditions. Atomic force microscopy and transmission electron microscopy revealed that the structural integrity of the methanoarchaeal cells is destroyed within 4 h after incubation with AMPs. The disruption of the cell envelope of M. smithii, M. stadtmanae, and M. mazei within a few minutes of exposure was verified by using LIVE/DEAD staining. Our results strongly suggest that the release of AMPs by eukaryotic epithelial cells is a potent defense mechanism targeting not only bacteria, but also methanoarchaea.

The Effect of Saturated Fatty Acids on Methanogenesis and Cell Viability ofMethanobrevibacter ruminantium

“…In detail, K + efflux was used as an indicator of membrane integrity. Finally, cell survival was monitored using the LIVE/DEAD BacLight Kit which has been successfully used in Archaea before [28, 29]. …”

Gut and Root Microbiota Commonalities

“…Lipopolysaccharide Rhizobium mutants that were more sensitive to maize antimicrobial benzoxazinones had reduced rhizospheric colonization (152). Antimicrobial peptides constitute a line of defense in plants as effectors of innate immunity and regulate not only bacteria but also methanogenic archaea in guts (153). Gut immunity determines bacterial composition; reciprocally, bacteria modulate host immunity in guts (154,155).…”

Development of Multiwell-Plate Methods Using Pure Cultures of Methanogens To Identify New Inhibitors for Suppressing Ruminant Methane Emissions

“…A microtiter plate method for performing antimicrobial peptide susceptibility testing has been reported for three different nonrumen methanogens (36). These methanogens were cultured with either methanol or H 2 -CO 2 (36). To specifically perform high-throughput screening of large compound libraries, we sought to develop a microtiter plate method that did not require H 2 overpressures for culturing rumen methanogens.…”

“…Both methanogens are typically grown using anaerobic culturing techniques in 5-ml or greater culture volumes using appropriately sealed and pressurized glass tubes, which is incompatible with modern high-throughput screening techniques for drug discovery and phenotypic analysis (35). A microtiter plate method for performing antimicrobial peptide susceptibility testing has been reported for three different nonrumen methanogens (36). These methanogens were cultured with either methanol or H 2 -CO 2 (36).…”