Chlamydomonas reinhardtii and Microbacterium forte sp. nov.,a mutualistic association that favor sustainable hydrogen production

Abstract

A multispecies bacterial community including Microbacterium fakhimi sp. nov., Stenotrophomonas goyi sp. nov., and Bacillus cereus greatly promoted sustained hydrogen production by the microalga Chlamydomonas reinhardtii when cocultivated in mannitol- and yeast extract-containing medium (up to 313 mLxx L-1). Alga viability was also largely prolonged in the cocultures (>45 days) without any nutrient supplementation. Among the bacterial community, Microbacterium fakhimi sp. nov. was the main responsible for the hydrogen production improvement. Nonetheless, the use of the entire bacterial community allowed a better growth of the alga during hydrogen production. Chlamydomonas reinhardtii and Microbacterium fakhimi sp. nov. established a mutualistic association, based on the release of ammonium and acetic acid from the bacterium, while the alga provided sulfur-containing metabolites and complemented the bacterial auxotrophy for biotin and thiamine. This study uncovers the potential of the Chlamydomonas-bacteria consortia for durable and stable H2 production while allowing the simultaneous production of biomass.

Stenotrophomonas goyi sp. nov., a novel bacterium associated with the alga Chlamydomonas reinhardtii

“…nov. genome has complete pathways for all the essential amino acids, is more likely that cysteine and methionine are being used as reduced S sources. Similar results were found for M. forte , where cysteine and methionine are required as S sources ( Fakhimi et al ., 2023a ).…”

“…A fortuitous contaminated Chlamydomonas reinhardtii culture (strain 704; CC-3597; https://www.chlamycollection.org/ ) was studied due to its enhanced hydrogen production capability. This alga culture turned out to be contaminated with three different bacterial strains ( Fakhimi et al ., 2023 ), one of them consisting in a white-pigmented bacterium ( Figure 1 ). This bacterium was isolated after several rounds of plate streaking in TYM medium.…”

“…nov. where it was isolated from a fortuitously contaminated Chlamydomonas reinhardtii culture in the laboratory. Initially, the Chlamydomonas reinhardtii culture was simultaneously contaminated with three different bacteria ( Fakhimi et al ., 2023a ). Individual members of this bacterial community were isolated by sequential rounds of plate streaking in Yeast Extract Mannitol (YEM) medium (handmade in our lab, described here ), until three different types of bacterial colonies were visually identified.…”

“…Colonies were grown separately, and the subsequent isolated DNA was used for PCR-amplification of their partial RNA 16S sequences. After sequencing, the three independently isolated bacteria were identified as members of the genus Microbacterium , Stenotrophomonas , and Bacillus ( Fakhimi et al ., 2023a ).…”

“…nov. isolated from a contaminated microalgae ( Chlamydomonas reinhardtii ) culture . This alga culture was simultaneously contaminated with S. goyi, Microbacterium forte ( Fakhimi et al ., 2023a ) and Bacillus cereus. The metabolic interactions established between these four microorganisms are analyzed and discussed in a related publication where the ability of this multispecies consortium to sustain hydrogen production is highlighted ( Fakhimi et al ., 2023a ).…”