Enterobacter tabaci 4M9 (CCB-MBL 5004) was reported to have plant growth-promoting and heavy metal tolerance traits. It was able to tolerate more than 300 mg/L Cd, 600 mg/L As, and 500 mg/L Pb and still maintained the ability to produce plant growth-promoting substances under metal stress conditions. To explore the genetic basis of these beneficial traits, the complete genome sequencing of 4M9 was carried out using Pacific Bioscience (PacBio) sequencing technology. The complete genome consisted of one chromosome of 4,654,430 bp with a GC content of 54.6% and one plasmid of 51,135 bp with a GC content of 49.4%. Genome annotation revealed several genes involved in plant growth-promoting traits, including the production of siderophore, indole acetic acid, and 1-aminocyclopropane-1-carboxylate deaminase; solubilization of phosphate and potassium; and nitrogen metabolism. Similarly, genes involved in heavy metals (As, Co, Zn, Cu, Mn, Se, Cd, and Fe) tolerance were detected. These support its potential as a heavy metal-tolerant plant growth-promoting bacterium and a good genetic resource that can be employed to improve phytoremediation efficiency of heavy metal-contaminated soil via biotechnological techniques. This, to the best of our knowledge, is the first report on the complete genome sequence of heavy metal-tolerant plant growth-promoting E. tabaci.
Antibiotic resistance in Gram-negative bacteria, particularly Salmonella and Shigella, requires surveillance worldwide. This study describes results of surveys in Hong Kong, Bangkok and Kuala Lumpur. All strains were isolated in hospitals which have large community catchment areas in addition to specialised hospital units. The prevalence of resistant strains was high in all areas. Gram-negative bacteria such as Enterobacter associated with hospital infections were resistant to penicillins and cephalosporins, with gentamicin resistance ranging from about 20% in Kuala Lumpur and Hong Kong, to 35% in Bangkok. Ninety-seven percent of Shigella isolated in Thailand were resistant to ampicillin. About 10% of Salmonella were resistant to chloramphenicol in all three centres.
The present study proposed the isolation of arsenic resistant bacteria from wastewater. Only three bacterial isolates (MNZ1, MNZ4 and MNZ6) were able to grow in high concentrations of arsenic. The minimum inhibitory concentrations of arsenic against MNZ1, MNZ4 and MNZ6 were 300 mg/L, 300 mg/L and 370 mg/L respectively. The isolated strains showed maximum growth at 37 °C and at 7.0 pH in control but in arsenite stress Luria Bertani broth the bacterial growth is lower than control. All strains were arsenite oxidizing. All strains were biochemically characterized and ribotyping (16S rRNA) was done for the purpose of identification which confirmed that MNZ1 was homologous to Enterobacter sp. while MNZ4 and MNZ6 showed their maximum homology with Klebsiella pneumoniae. The protein profiling of these strains showed in arsenic stressed and non stressed conditions, so no bands of induced proteins appeared in stressed conditions. The bacterial isolates can be exploited for bioremediation of arsenic containing wastes, since they seem to have the potential to oxidize the arsenite (more toxic) into arsenate (less toxic) form.