L. Paikhomba Singha

Shape dependent physical mutilation and lethal effects of silver nanoparticles on bacteria

In this report, spherical silver nanoparticle (AgNP-sp) and rod-shaped silver nanoparticle (AgNR) were prepared by chemical reduction method and their antibacterial activity against various Gram-positive and Gram-negative bacteria had been evaluated for their efficiency. Minimal inhibitory concentration (MIC) tests were conducted to study the antibacterial properties, and substantiated with killing kinetics of silver nanoparticles (AgNPs). The study revealed that both AgNP-sp and AgNRs are good antibacterial candidates. Bacterial sensitivity to nanoparticles (NPs) was found to vary depending on microbial species. Disc diffusion studies revealed the greater effectiveness of AgNP-sp and AgNR against Klebsiella pneumoniae AWD5 at the doses of 249 and 392 µg. The dose dependent activities of prepared NPs were also observed on the batch studies of disc diffusion and MIC with various strains. The optical and morphological structures of NPs were analyzed by UV-visible, XRD, FE-SEM and TEM. Further, FESEM of bacterial culture treated with AgNPs confirmed antibacterial activity of NPs by showing rupture of bacterial cell wall. Also, the genome of test organism was found to have CusCFBA and CusRS operons. The killing kinetics confirmed that the death rate of K. pneumoniae was higher against AgNP-sp as compared to AgNR.

Draft Genome Sequence of Klebsiella pneumoniae AWD5

ABSTRACT Here, we report the draft genome sequence of Klebsiella pneumoniae strain AWD5, isolated from an automobile workshop in India. The de novo assembly resulted in a 4,807,409 bp genome containing 25 rRNA genes, 81 tRNAs, and 4,636 coding sequences (CDS). It carries important genes for polyaromatic hydrocarbon degradation and benzoate degradation.

Erratum for Rajkumari et al., “Draft Genome Sequence of Klebsiella pneumoniae AWD5”

Volume 5, no. 5, e01531-16, 2017, [https://doi.org/10.1128/genomeA.01531-16][1]. Page 1, line 35: “65.96%” should read “58.18%.” [1]: /lookup/doi/10.1128/genomeA.01531-16

Rhizoremediation prospects of Polyaromatic hydrocarbon degrading rhizobacteria, that facilitate glutathione and glutathione-S-transferase mediated stress response, and enhance growth of rice plants in pyrene contaminated soil

Rhizoremediation is a strategy where pollutant degrading bacteria are augmented through plant roots using plant-microbe interaction. Therefore, for effective rhizoremediation of pyrene contaminated soil, bacterial strains were experimented for amelioration of stress response in host plant along with biodegradation ability. A total of 28 bacteria, having ability to degrade polycyclic aromatic hydrocarbons were isolated from contaminated sites and checked for their plant growth promoting attributes, such as indole acetic acid (IAA) production, phosphate solubilization, atmospheric nitrogen fixation and siderophore release. Among these isolates, Klebsiella pneumoniae AWD5 was found to degrade 60% of pyrene. While other isolates, i.e. Alcaligenes faecalis BDB4, Pseudomonas fragi DBC, Pseudomonas aeruginosa PDB1, Acinetobactor sp. PDB4 degraded 48.5%, 50.29%, 31.3% and 36% of pyrene, respectively, after 6 days of incubation. K. pneumoniae AWD5 produced 94.2 μg/ml IAA and 3.1 mM/mg/h unit of ACC deaminase, which was best among eighteen indole acetic acid producers and five of the 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing isolates. P. aeruginosa PDB1 resulted in highest phosphate solubilization activity of 875.26 ng/ml of soluble phosphate among seven phosphate solubilizers. The isolates AWD5 and PDB1 both have shown a good amount of siderophore release (56.3% and 84.3% unit). There was 19.1% increase in shoot length of rice seedlings treated with PDB1 in presence of pyrene. Similarly, 26.5% increase in the root length of AWD5 treated rice was recorded in pyrene contaminated soil. Bacterial inoculation also induced and improved the stress response in host plant, in presence of pyrene, as suggested by the superoxide dismutase, glutathione and glutathione-S-transferase activities in rice.