Isolation and Characterization of a Molybdenum-reducing and Carbamate-degrading Serratia sp. strain Amr-4 in soils from Egypt

Physical or chemical procedures could efficiently remove contaminants including pesticides such as carbamates from high concentrations of toxicants. Bioremediation, on the other hand, is frequently a less expensive option in the long term when used at low concentrations. Isolation of multiple toxicants removing microorganisms is the goal of bioremediation. In this paper we report on the molybdenum reduction of the bacterium and its ability to grow on the carbamates carbofuran and carbaryl as carbon sources. Both the carbamates carbofuran and carbaryl cannot support molybdenum reduction when used as the sole carbon sources. Between pH 6.0 and 6.8 and between 30 and 34 oC, the bacterium is most efficient in converting molybdate to Mo-blue. For molybdate reduction, glucose was shown to be the strongest electron donor, with maltose and sucrose coming in second and third, respectively, and d-mannitol and d-adonitol coming in last. Phosphate concentrations of 2.5 to 7.5 mM and molybdate concentrations of 20 to 30 mM are also needed. Identical to that of a decreased phosphomolybdate, the Mo-blue produced by the new Mo-reducing bacteria has an absorption spectrum similar to prior Mo-reducing bacteria. Inhibition of molybdenum reduction was 73.3, 50.1, 50.1 and 20.7 percent, respectively, by mercury, copper, silver and lead at 2 ppm. The bacterium was tentatively identified as Serratia sp. strain Amr-4 after biochemical investigation. This bacterium's ability to detoxify a variety of toxicants is highly sought after, making it a significant bioremediation agent.

Disintegration promotes protospacer integration by the Cas1-Cas2 complex

‘Disintegration’—the reversal of transposon DNA integration at a target site—is regarded as an abortive off-pathway reaction. Here, we challenge this view with a biochemical investigation of the mechanism of protospacer insertion, which is mechanistically analogous to DNA transposition, by the Streptococcus pyogenes Cas1-Cas2 complex. In supercoiled target sites, the predominant outcome is the disintegration of one-ended insertions that fail to complete the second integration event. In linear target sites, one-ended insertions far outnumber complete protospacer insertions. The second insertion event is most often accompanied by the disintegration of the first, mediated either by the 3′-hydroxyl exposed during integration or by water. One-ended integration intermediates may mature into complete spacer insertions via DNA repair pathways that are also involved in transposon mobility. We propose that disintegration-promoted integration is functionally important in the adaptive phase of CRISPR-mediated bacterial immunity, and perhaps in other analogous transposition reactions.