Tetracycline and 4-epitetracycline modified thein vitrocatabolic activity and structure of a sediment microbial community from a tropical tilapia farm idiosyncratically

Abstract

Aquaculture farmers commonly add tetracycline to fish feed or to their ponds to prevent or treat bacterial infections in their crops. To assess the short-term effect of tetracycline (TET) and of one of its reversible epimers, 4-epitetracycline (ETC), on the function and structure of a sediment microbial community from a tropical tilapia farm, we contrasted community-level physiological profiles (CLPP) and phospholipid fatty acid profiles (PLFA) obtained from microcosms exposed for 12 days to 5, 10, 50, or 75 mg kg(-1)of these antibiotics. Notwithstanding that the concentration of the antibiotics during the experiment decreased between 13-100% (TET) or 16-61% (ETC), both compounds provoked opposing metabolic responses that did not revert. TET displayed a tendency to inhibit respiration at concentrations < 50 mg kg(-1), whereas ETC showed the opposite effect. As revealed by the finding of the fatty acids 11:0 iso 3OH, 16:1w6c, and 18:1w6c, the sediment analyzed was predominantly colonized by Gram-negative bacteria. A marked decrease in fatty acid diversity accompanied the aforementioned metabolic responses, with TET concentrations > 50 mg kg(-1)leading to an enrichment of yeast and fungal biomarkers and both antibiotics at concentrations < 10 mg kg(-1)selecting for microorganisms with 11:0 iso 3OH. In agreement with CLPP data, differences between the PLFA profiles of control and treated microcosms were more pronounced for TET than for ETC. We conclude that high, yet field-relevant, concentrations of TET and ETC have the potential to modify the composition, and to a lesser extent, the functioning of a sediment microbial community. This study highlights the importance of considering antibiotic degradation products in ecotoxicological research.

Ecotoxicological assessment of antibiotics: A call for improved consideration of microorganisms

“…Analyzing the amounts and types of PLFAs in environmental samples is associated with the abundance of these groups, and is thus a useful method for elucidating the microbial composition in environmental samples at a very coarse level. PLFA analysis has been used to study the effects of antibiotics in environmental matrices including sediments, salt marshes and soils (Cordova-Kreylos and Scow, 2007;Demoling et al, 2009;Granados-Chinchilla et al, 2013;Hammesfahr et al, 2008). Although PLFA fingerprinting is a robust method with some attractive features (Frostegård et al, 2011) the method has disadvantages for ERA of antibiotics.…”

A single exposure of sediment sulphate-reducing bacteria to oxytetracycline concentrations relevant to aquaculture enduringly disturbed their activity, abundance and community structure

“…The functional, structural and genetic effects reported here took place despite the fact that OTC partially disappeared, confirming that 4‐EOTC—and possibly other OTC derivatives—retain some degree of biological activity in sediments (Blackwood and English ; Granados‐Chinchilla et al . ). These findings highlight the importance of considering antibiotic metabolites and epimers in studies dealing with the ecotoxicology of drugs.…”

“…; Granados‐Chinchilla et al . ), we hypothesized that exposure of a pond sediment to OTC would alter the activity, abundance and diversity of its SRB community. Our culture‐dependent (plate counts) and culture‐independent experiments qPCR and fluorescent in situ hybridizations (FISH) confirmed our hypothesis, as a single exposure to this drug decreased the SO 4 2− reducing activity and the number of copies of dsrB in the sediment within 3 days and changed the composition of the SRB community until day 30.…”

“…Based on the known structural and functional effects of OTC on communities of environmental aerobic bacteria (Klaver and Matthews 1994;Thiele-Bruhn and Beck 2005;Piotrowska-Seget et al 2008;K€ ummerer 2009;Liu et al 2009a;Yang et al 2009;Granados-Chinchilla et al 2013), we hypothesized that exposure of a pond sediment to OTC would alter the activity, abundance and diversity of its SRB community. Our culture-dependent (plate counts) and culture-independent experiments qPCR and fluorescent in situ hybridizations (FISH) confirmed our hypothesis, as a single exposure to this drug decreased the SO 4 2À reducing activity and the number of copies of dsrB in the sediment within 3 days and changed the composition of the SRB community until day 30.…”

“…OTC degradation and 4-EOTC appearance were followed for 30 days using a published HPLC method (Granados-Chinchilla et al 2013). Briefly, sediment samples of 25 g each, collected on days 3, 12, 21 and 30 p.o.e., were extracted with 40 ml of a methanolic solution containing citric acid (0Á5 g 100 ml À1 ) using an Ultraturrax homogenizer (IKA Works, Staufen, Germany).…”