Microorganisms Involved in Hydrogen Sink in the Gastrointestinal Tract of Chickens

Abstract

Hydrogen sink is a beneficial process, which has never been properly examined in chickens. Therefore, the aim of this study was to assess the quantity and quality of microbiota involved in hydrogen uptake with the use of real-time PCR and metagenome sequencing. Analyses were carried out in 50 free-range chickens, 50 commercial broilers, and 54 experimental chickens isolated from external factors. The median values of acetogens, methanogens, sulfate-reducing bacteria (SRB), and [NiFe]-hydrogenase utilizers measured in the cecum were approx. 7.6, 0, 0, and 3.2 log₁₀/gram of wet weight, respectively. For the excreta samples, these values were 5.9, 4.8, 4, and 3 log₁₀/gram of wet weight, respectively. Our results showed that the acetogens were dominant over the other tested groups of hydrogen consumers. The quantities of methanogens, SRB, and the [NiFe]-hydrogenase utilizers were dependent on the overall rearing conditions, being the result of diet, environment, agrotechnical measures, and other factors combined. By sequencing of the 16S rRNA gene, archaea of the genus Methanomassiliicoccus (Candidatus Methanomassiliicoccus) were discovered in chickens for the first time. This study provides some indication that in chickens, acetogenesis may be the main metabolic pathway responsible for hydrogen sink.

Keywords: Campylobacter jejuni; Methanomassiliicoccus; acetogens; chicken gut microbiota; hydrogen uptake; methanogenic archaea; sulfate-reducing bacteria.

Figure 1

(A–F). Box plots representing the abundance of selected microbial groups in ceca and excreta samples. Statistical significance between cecal contents and excreta is marked by asterisks. Values of ** p < 0.01, and *** p < 0.001 were regarded as significant; ns: non-significant.

Figure 2

(A–F). Box plots representing the abundance of selected microbial groups in three rearing systems. Statistical significance among the three groups is marked by asterisks. Values of * p < 0.05, and *** p < 0.001 were regarded as significant; ns: non-significant.

Figure 3

(A–F). Box plots representing the abundance of selected microbial groups across age groups in the commercial chickens. Statistical significance among the age groups is marked by asterisks. Values of * p < 0.05, and ** p < 0.01 were regarded as significant. The non-significant results remained unmarked.

Figure 4

(A–F). Box plots representing the abundance of selected microbial groups across age groups in the experimental farm chickens. Statistical significance among age groups is marked by asterisks. Values of * p < 0.05, ** p < 0.01, and *** p < 0.001 were regarded as significant. The non-significant results remained unmarked.