Effect of Glucose on the Fatty Acid Composition of Cupriavidus necator JMP134 during 2,4-Dichlorophenoxyacetic Acid Degradation: Implications for Lipid-Based Stable Isotope Probing Methods

Abstract

Combining lipid biomarker profiling with stable isotope probing (SIP) is a powerful technique for studying specific microbial populations responsible for the degradation of organic pollutants in various natural environments. However, the presence of other easily degradable substrates may induce significant physiological changes by altering both the rate of incorporation of the target compound into the biomass and the microbial lipid profiles. In order to test this hypothesis, Cupriavidus necator JMP134, a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium, was incubated with [ 13 C]2,4-D, [ 13 C]glucose, or mixtures of both substrates alternatively labeled with 13 C. C. necator JMP134 exhibited a preferential use of 2,4-D over glucose. The isotopic analysis showed that glucose had only a small effect on the incorporation of the acetic chain of 2,4-D into the biomass (at days 2 and 3) and no effect on that of the benzenic ring. The addition of glucose did change the fatty acid methyl ester (FAME) composition. However, the overall FAME isotopic signature reflected that of the entire biomass. Compound-specific individual isotopic analyses of FAME composition showed that the 13 C-enriched FAME profiles were slightly or not affected when tracing the 2,4-D acetic chain or 2,4-D benzenic ring, respectively. This batch study is a necessary step for validating the use of lipid-based SIP methods in complex environments.

Biofilm vs. Planktonic Lifestyle: Consequences for Pesticide 2,4-D Metabolism by Cupriavidus necator JMP134

“…The similarity of the total FAME amounts in both treatments (with or without sand) suggested that there was no difference in the total microbial biomass. Spectrophotometric measurements of the bacterial density in the liquid phase showed that C. necator JMP134 cultures in the presence of 2,4-D presented similar growth as reported previously (Lerch et al, 2007 , 2011 ). For both treatments, the exponential phase reached its maximum after 3 days followed by a stationary phase that lasted for the next 2 days.…”

“…Variations in the lipid biomarker composition are not only due to the modification of the microbial composition but also to physiological changes. For example, the sensitivity of FAME profiles to change in growth substrate has been reported (Lerch et al, 2011 ). According to the present study, the bacterial sessile mode of life also alters the signature of lipid biomarkers.…”

“…In the present study, we hypothesize that adding sand grains to a culture will induce the development of a microbial biofilm that might change the bacterial metabolic activity and/or the retention of 2,4-D. We combined classical optical density measurements, respirometry, microscopy and isotopic analysis. The fatty acid composition of C. necator JMP134 has been reported to be modified by the nature of the growth substrate (Lerch et al, 2011 ). We expect that such potential change in fatty acid profiles and isotopic signature could also occur with the biofilm formation.…”

Rapid Biodegradation of the Herbicide 2,4-Dichlorophenoxyacetic Acid by Cupriavidus gilardii T-1

“…Up to now, a number of bacterial strains utilizing 2,4-D have been reported, such as A. xylosoxidans EST4002, 23 Arthrobacter sp., 35 Bradyrhizobium sp. HW13, 36 B. elkanii USDA94, 37 Burkholderia cepacia DS-1, 17 C. necator JMP134, 28 C. campinensis BJ71, 38 Cupriavidus sp. TFD33, 39 Novosphingobium DY4, 40 Pseudomonas sp.…”

“…3,26 C. necator JMP134 could degrade 70% of 2,4-D at 250 mg L −1 in 10 days, and its degradation rate was 17.5 mg L −1 day −1 . 28 Although numerous strains have been reported to degrade 2,4-D, it would be still valuable for acquiring novel and fast…”