Syntrophic Interactions Within a Butane-Oxidizing Bacterial Consortium Isolated from Puguang Gas Field in China

Abstract

Butane oxidation by the hydrocarbon degradation bacteria has long been described, but little is known about the microbial interaction in this process. To investigate this interaction, the efficiency of butane oxidation was estimated in monocultures and co-cultures of six strains of butane-oxidizing bacteria (BOB) and a butanol-oxidizing strain. Results showed that the butane degradation velocity was at least 26 times higher in the co-culture of the seven strains (228.50 nmol h(-1)) than in the six individual monocultures (8.71 nmol h(-1)). Gas chromatographic analysis of metabolites in the cultures revealed the accumulation of butanol in the monocultures of BOB strains but not in the co-culture with the butanol-oxidizing strain. These results evidenced a novel syntrophic association between BOB and butanol-oxidizing bacteria in the butane oxidation. The BOB strains oxidized butane into butanol, but this activity was inhibited by the accumulated butanol in monocultures, whereas the removal of butanol by the butanol-oxidizing strain in co-culture could eliminate the suppression and improve the butane degradation efficiency. In the co-culture, both BOB and butanol-oxidizing bacteria could grow and the time needed for butane complete removal was shortened from more than 192 h to less than 4 h. The unsuppressed effect of the co-culture was also consistent with the results of reverse transcription quantitative real-time PCR (RT-qPCR) of bmoX gene because increased expression of this gene was detected during the syntrophic growth compared with that in monoculture, pointing to the upregulation of bmoX in the syntrophic interaction.

Novel Butane-Oxidizing Bacteria and Diversity of bmoX Genes in Puguang Gas Field

“…We also found that bmoX genes were associated with butane degradation in G samples, as the increased abundance of bmoX genes in the G samples ( Figure 4 ) was positively correlated with the significant butane degradation taking place in the G microcosms (Supplementary Table S1 ). Zhang Y. et al (2016) observed a similar phenomenon, i.e., bmoX genes were upregulated as the butane degradation rate increased. High concentrations of oil might be toxic to microbes ( Samanta et al, 2002 ), and therefore, many studies have reported that oil contamination decreases the diversity of microorganisms and the relevant functional genes in a variety of environments ( Liang et al, 2011 ; Bell et al, 2013 ; Yang et al, 2014 ).…”

“…Gammaproteobacteria species from the genus Pseudomonas is widespread in the natural environment and is able to metabolize a wide range of organic compounds ( Salgado-Brito et al, 2007 ; Dong et al, 2015 ; Baruah et al, 2016 ; Hemidouche et al, 2016 ), including light hydrocarbons ( Zhang Y. et al, 2016 ). For this reason, Pseudomonas was entrusted with the task of biodegrading hydrocarbon pollutants in contaminated sites, as well as serving as a biological indicator of oil and gas reservoirs.…”

“…The first step in butane removal is the oxidization of butane into butanol by monooxygenases, therefore, the accumulation of butanol inhibited butane degradation. Moreover, the degradation ability of BOB is related to their tolerance to butanol ( Zhang Y. et al, 2016 ). The decrease of bomX abundance in NG sample after 6 days of incubation (Supplementary Figure S4 ) might be explained by the possibility that butane stimulated the growth of bomX -harboring bacteria in NG sample, which oxidize the butane into butanol.…”

“…The bmoX gene, encoding the alpha hydroxylase subunit of BMO (BmoX) classified into the group 3 SDIMOs ( Coleman et al, 2006 ), is a conserved gene segment and its insertional mutation in a P. butanovora strain results in the loss of the ability to grow on butane ( Sluis et al, 2002 ). Zhang Y. et al (2016) reported that the expression level of bmoX genes can reflect the butane-oxidizing activity of BOB. Despite the importance of the bmoX gene in butane oxidation, its sequence diversity and distribution in BOB species have been rarely studied.…”

A Novel Culturing Chip (cChip) Can Facilitate Culturing of Unculturable Bacteria From Aquatic Environment

“…Besides, we use concentration of microbes after retaining them on the lter paper, therefore, there is a possibility of the presence of helper species which can be a facilitating factor for growth of those microorganisms that have been previously uncultured. Different studies have proven in the past years that the presence of some microorganisms and sometimes a small distance between the two microorganisms like less than 2µm facilitates the growth of microorganisms in co-culture [47][48][49]. We would like to explore these synergistic relationships in future.…”