Seasonal bacterial community dynamics in a crude oil refinery wastewater treatment plant.

The biological treatment of oil refinery effluents in wastewater treatment plants (WWTPs) relies on specialized bacteria contributing to remove organic load, nitrogen, sulfur, and phosphorus compounds. Knowledge about bacterial dynamics in WWTPs and how they affect the performance of the wastewater treatment is limited, particularly in tropical countries. The bacterial communities from three compartments of an oil refinery WWTP in Uran, India, were assessed using 16S-metabarcoding, in winter and monsoon seasons, upstream (from the surge pond) and downstream the biotower (clarifier and guard pond), to understand the effects of seasonal variations in WWTP's efficiency. The organic load and ammonia levels of the treated wastewater increased by 3- and 9-fold in the monsoon time-point. A decreased abundance and diversity of 47 genera (325 OTUs) comprising ammonia and nitrite oxidizing bacteria (AOB, NOB, denitrifiers) was observed in the monsoon season downstream the biotower, whereas 23 OTUs of Sulfurospirillum, Desulfovibrio, and Bacillus, putatively performing dissimilatory nitrate reduction to ammonia (DNRA), were 3-fold more abundant in the same compartments (DNRA/denitrifiers winter ratio < 0.5 vs. monsoon ratio around 3). The total abundance of reported sulfate- and sulfite-reducing bacteria also increased 250- and 500-fold downstream the biotower, in the monsoon time-point. Bacteria performing DNRA may thus outcompete denitrification in this WWTP, limiting the biodegradation process. The alterations detected in bacterial populations involved in the removal of nitrogen and sulfur species evidenced a reduced quality of the released wastewater and may be good candidates for the following monitoring strategies and optimization of the wastewater treatment.

Draft genome sequence of atrazine-utilizing bacteria isolated from Indian agricultural soil.

We report the draft genome sequences of two tropical bacterial isolates capable of degrading the herbicide atrazine. Alcaligenes sp. strain EGD-AK7 and Arthrobacter sp. strain AK-YN10 were isolated from Indian agricultural soil in which sugarcane is grown, with a reported history of atrazine use. EGD-AK7 has the atzABCDEF genes and AK-YN10 has the trzN and atzBC genes for atrazine degradation.