Silver nanoparticles induced with aqueous black carpenter ant extract selectively inhibit the growth of Pseudomonas aeruginosa.

Aqueous black carpenter ant extract (ABCAE) was used to synthesize silver nanoparticles (AgNPs). The ABCAE was rich in water-soluble compounds such as hydrophilic polypeptides that behaved as both reducing and stabilizing agents for generating AgNPs from Ag+ ion precursors. The diameter of the observed AgNPs was mostly in the range of 20-60 nm. The AgNPs were tested as an antibacterial agent for the growth inhibition of two pathogenic bacteria (Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 27661) and one common bacteria (Escherichia coli K12 ATCC 10798). Disk diffusion test showed that the AgNPs selectively inhibited the growth of P. aeruginosa but not for the other two species, suggesting the potential application of the green-chemically synthesized AgNPs as a selective antibacterial agent without harming other beneficial bacteria.

Synergistic effect of crude oil plus dispersant on bacterial community in a louisiana salt marsh sediment.

A combined effect of crude oil plus dispersant (Corexit 9500A) significantly altered indigenous bacterial communities in a Louisiana salt marsh sediment after 30 days of incubation; the crude oil and/or Corexit 9500A treatments triggered shifts in bacterial communities and the shifted bacterial structure by crude oil plus Corexit 9500A was considerably different from those by either crude oil or Corexit 9500A. However, the synergistic effect of crude oil plus Corexit 9500A was not observed after 7 days of incubation; the bacterial community was slightly shifted by Corexit 9500A and the crude oil did not trigger any bacterial community shift after 7 days of incubation. DNA sequencing data indicated that Chromobacterium species was enriched in the Corexit 9500A microcosms after 7 days of incubation, while Pseudomonas, Advenella, Acidocella and Dyella spp. were enriched after 30 days of incubation. Parvibaculum was a dominant species in the crude oil microcosms after 30 days of incubation. Rhodanobacter, Dyella and Frateuria spp. were dominant in crude oil plus Corexit 9500A microcosms after 30 days of incubation. Our data show that the effect of crude oil plus Corexit 9500A on bacterial community is synergistic, and thus the dispersant effect should be considered with the spilled oil to correctly evaluate the environmental impact.