The effect of the sulfonamide class of antibiotics, namely, trimethoprim and sulfamethoxazole (TMP–SMX) on growth and metabolism of a bacterial consortium isolated from an anaerobic digester of a sewage treatment plant, was investigated. The bacterial consortium was exposed to various concentrations of TMP–SMX. The results indicated that there was no effect of TMP and SMX on the bacterial consortium in terms of bacterial growth and carbon and nitrate removal even at the highest concentration tested at 250 mg/L. The carbon removal was more than 90%, and the nitrate removal was more than 87% in all culture conditions. A pure culture was isolated and identified as Leuconostoc mesenteroides from the consortium, which was able to use TMP and SMX as the sole source of carbon for growth. This pure culture has the sul1 gene to show resistance to these antibiotics. This research could be used in the anaerobic digestion process to degrade various classes of sulfonamide antibiotics before the treated sludge is discharged into the environment to reduce the concentration of TMP and SMX.

Nanoparticle (NP) use in engineering, medicine, cosmetics, personal care products, and manufacturing is becoming more common resulting in a significant increase in accumulation in biological systems and have been shown to have disruptive and antimicrobial effects. Nanoparticle accumulation will disrupt the natural biogeochemical cycles such as carbon and nitrogen cycles by inhibiting microbes that participate in these cycles. The purpose of this study was to determine the effect of silver oxide nanoparticles on carbon and nitrogen cycles in the sediment bacteria isolated from the Gulf of Mexico of the coast of the state of Louisiana in the USA. A bacterial consortium developed from the coastal Louisiana was exposed to various concentrations of silver oxide nanoparticles. The results showed that the silver oxide NP at concentrations 4 mg/L or above were lethal to the bacteria, and bacterial growth was inhibited resulting in significant loss of carbon and nitrogen removal activities of the bacterial consortium. The lethal concentration 50 (LC50) of silver oxide NP for the coastal bacteria was found to be 3.07 mg/L. The bacterial consortium was stressed at higher doses above 2 mg/L of NP leading to excess production of extracellular polymeric substances.

Metagenomics and transcriptomics have had some success analyzing community and functional ecology of the termite gut, but carbon utilization ecology and the effect of diet on the gut community are not well understood. This study was done to determine the effect of three hardwood tree types, oak (Quercus spp.), red maple (Acer rubrum), and tupelo (Nyssa aquatica) on the termite species, Reticulitermes flavipes in the family Rhinotermitidae. Termite abdomen homogenates were incubated on agar plates containing three common carbon sources in the termite gut, namely, acetate, cellobiose, and phenol under aerobic and anaerobic conditions. Bacterial growth was higher on cellobiose than any other carbon source. Higher bacterial growth on cellobiose was observed from termite colonies feeding on oak than on phenol from the other two wood types. The difference between aerobic and anaerobic conditions was not significant. A bacterium, Acinetobacter tandoii isolated and identified from our previous study was subjected to high concentrations of phenol as the sole carbon source and this bacterium was able to degrade phenol concentration up to 600 mg/L.