Effects of copper on expression of methane monooxygenases, trichloroethylene degradation, and community structure in methanotrophic consortia

Abstract

Copper plays a key role in regulating the expression of enzymes that promote biodegradation of contaminants in methanotrophic consortia (MC). Here, we utilized MC isolated from landfill cover to investigate cometabolic degradation of trichloroethylene (TCE) at nine different copper (Cu2+) concentrations. The results demonstrated that an increase in Cu2+ concentration from 0 to 15 μM altered the specific first‐order rate constant k1,TCE, the expression levels of methane monooxygenase (pmoA and mmoX) genes, and the specific activity of soluble methane monooxygenase (sMMO). High efficiency TCE degradation (95%) and the expression levels of methane monooxygenase (MMO) were detected at a Cu2+ concentration of 0.03 μM. Notably, sMMO‐specific activity ranged from 74.41 nmol/(mgcell h) in 15 μM Cu2+ to 654.99 nmol/(mgcell h) in 0.03 μM Cu2+, which contrasts with cultures of pure methanotrophs in which sMMO activity is depressed at high Cu2+ concentrations, indicating a special regulatory role for Cu2+ in MC. The results of MiSeq pyrosequencing indicated that higher Cu2+ concentrations stimulated the growth of methanotrophic microorganisms in MC. These findings have important implications for the elucidation of copper‐mediated regulatory mechanisms in MC.

Genetical and Biochemical Basis of Methane Monooxygenases of Methylosinus trichosporium OB3b in Response to Copper

“…Previous research has reported a correlation between methane oxidation rates in Ob3b and increasing concentrations of Cu in the growth medium as well as the expression of MMOs [34][35][36][37]. Similarly, this study observed an enhancement in the methane and oxygen utilization rates for each concentration of Cu used to grow the M. trichosporium OB3b, as depicted in Figure 1b and c, respectively.…”

“…These results suggest that an increase in the rate of methane uptake is directly proportional to the increased growth rates and Cu concentration in the culture medium. As such, published reports have suggested that methane uptake rates may continue to increase until the Cu concentration reaches to a toxic concentration (>4.2 mM) for most well-studied methanotrophs [12,35,38].…”

“…Han et al have shown that the expression of sMMO in methanotrophs is efficient at Cu concentrations of less than 0.8 µM and is restricted at an excess of 4 µM Cu [46]. However, Xing et al used methanotrophic consortia and found that there was no such repression at a 4 µM Cu concentration [35]. Brusseau et al reported that at above a 0.25 µM Cu concentration, M. trichosporium OB3b cells did not show any sMMO activity [47].…”

Environmental and Microbial Interactions Shape Methane-Oxidizing Bacterial Communities in a Stratified Lake

“…Heterotrophic richness has been shown to enhance methane oxidation activity by MOB (Ho et al, 2014), as accompanying organisms can either remove inhibiting substances (e.g., methanol) or provide stimulating factors (e.g., essential nutrients such as cobalamin; Stock et al, 2013;Iguchi et al, 2015;Veraart et al, 2018;Singh et al, 2019). On the other hand, MOB also select for certain heterotrophs by providing organic metabolites (e.g., acetate) or by removing toxic compounds (e.g., formaldehyde; Morris et al, 2013;van der Ha et al, 2013;Oshkin et al, 2015;Gilman et al, 2017;Xing et al, 2018). Indeed, MOB play an integral role in transferring methane-derived carbon and other metabolites to the microbial pool and higher trophic levels of the food web (Jones and Grey, 2011;Sanseverino et al, 2012;Agasild et al, 2014).…”

Active Methanotrophs and Their Response to Temperature in Marine Environments: An Experimental Study

“…Although variations in temperature resulting from seasonal fluctuations may be quite limited and the bottom water temperature is usually stable (2-7 • C) for deep marine environments, it may be influenced by ocean currents [26]. The temperature sensitivity of methanotrophs is susceptible to other environmental factors, such as water content and sediment characteristics [27][28][29], and thus, the response of aerobic methane oxidation patterns to temperature in terrestrial ecosystems such as rice fields, forests, or permafrost soils may be quite different from that in marine environments [30,31]. Currently, exact knowledge regarding temperature controls on marine aerobic methane oxidation is still missing.…”