Effect of Sulfadiazine-Contaminated Pig Manure on the Abundances of Genes and Transcripts Involved in Nitrogen Transformation in the Root-Rhizosphere Complexes of Maize and Clover

Abstract

The antibiotic sulfadiazine (SDZ) can enter the environment by application of manure from antibiotictreated animals to arable soil. Because antibiotics are explicitly designed to target microorganisms, they likely affect microbes in the soil ecosystem, compromising important soil functions and disturbing processes in nutrient cycles. In a greenhouse experiment, we investigated the impact of sulfadiazine-contaminated pig manure on functional microbial communities involved in key processes of the nitrogen cycle in the rootrhizosphere complexes (RRCs) of maize (Zea mays) and clover (Trifolium alexandrinum). At both the gene and transcript level, we performed real-time PCR using nifH, amoA (in both ammonia-oxidizing bacteria and archaea), nirK, nirS, and nosZ as molecular markers for nitrogen fixation, nitrification, and denitrification. Sampling was performed 10, 20, and 30 days after the application. SDZ affected the abundance pattern of all investigated genes in the RRCs of both plant species (with stronger effects in the RRC of clover) 20 and 30 days after the addition. Surprisingly, effects on the transcript level were less pronounced, which might indicate that parts of the investigated functional groups were tolerant or resistant against SDZ or, as in the case of nifH and clover, have been protected by the nodules.

Effects of repeated application of sulfadiazine-contaminated pig manure on the abundance and diversity of ammonia and nitrite oxidizers in the root-rhizosphere complex of pasture plants under field conditions

“…Similar results have been reported in analyses of bulk soil (Schauss et al, 2009) and in the rhizosphere of agricultural crops (Ollivier et al, 2010). These results demonstrate that SDZ inhibits the growth of AOB populations (considering gene abundance as proxy).…”

“…From this time point onward, the amoA AOB and AOA gene abundance patterns were decreased and increased, respectively (Figure 2). Although it has been already shown that AOA were impacted to a lower extent by SDZ than AOB in greenhouse experiments (Schauss et al, 2009; Ollivier et al, 2010), in this study we observed for the first time a significant increase in amoA AOA gene copies ( P = 0.005 at day 56) while amoA AOB gene copies were significantly decreased ( P = 0.005 and P = 0.013 at day 49 and 63, respectively) with PMSDZ treatment, confirming the potential occurrence of functional redundancy between the two communities under antibiotic stress (Schauss et al, 2009). However, caution must be taken when relating significant impacts of the antibiotic on the gene level to associated functions.…”

Exposure to vancomycin causes a shift in the microbial community structure without affecting nitrate reduction rates in river sediments

“…Ollivier et al (2010) reported that the abundance of nosZ was affected by sulfadiazine but the impact on the transcript level was less pronounced, suggesting that a part of the denitrifiers was tolerant or resistant towards this antibiotic. In soils amended with manure and sulfadiazine (SDZ, 40 and 100 mg SDZ kg −1 soil), the community composition of nirS nitrite reducers investigated by DGGE did not change despite the observed alterations in abundance .…”

“…The impact of antibiotics on denitrifying bacteria has been assessed mainly through the quantification of genes encoding the nitrate, nitrite and nitrous oxide reductases and diversity analysis of these genes by DGGE Ollivier et al 2010;Hammesfahr et al 2008). Ollivier et al (2010) reported that the abundance of nosZ was affected by sulfadiazine but the impact on the transcript level was less pronounced, suggesting that a part of the denitrifiers was tolerant or resistant towards this antibiotic.…”

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

“…Bioinformatics and computational constraints represent other important challenges (Gilbert et al, 2011). We strongly encourage further basic research in this field for instance with a focus on transcriptional dynamics of specific functional genes that can be related to specific ecosystem services provided by microorganisms (Table 3; Table S1; Ollivier et al, 2010).…”