Shifts in metabolic patterns of soil bacterial communities on exposure to metal engineered nanomaterials.

The explosive growth in nanomaterial use will bring about their increased release into terrestrial ecosystems. Metal engineered nanomaterials (ENMs) that gain entry into these environments may alter the composition and activities of resident natural bacterial communities. To assess changes in community level physiological profiles (CLPP) of microbial communities in soils exposed to metal ENMs, Biolog EcoPlates were used in this exploratory comparative study. The CLPP is a rapid screening technique to characterise functional differences among heterotrophic microbial communities based on variable substrate utilization. The impacts of three metal ENMs, silver, titanium dioxide and zinc oxide, on bacterial communities were investigated using three soil types from Maharashtra, India. Metabolic diversity of bacterial communities was impacted in the soils in presence of silver and zinc oxide, but not in presence of titanium dioxide nanoparticles. Diversity indices, viz., Shannon's index, Evenness index and Simpson's index also showed significant differences in the presence of silver and zinc oxide nanoparticles. Principal component analysis revealed changes in metabolic profiles in the presence of silver nanoparticles. This study also shows that testing ecotoxicity of nanoparticles using readily culturable bacteria is a practical approach.

Mechanical, antibacterial and biodegradable properties of starch film containing bacteriocin immobilized crystalline nanocellulose.

We reported the preparation of antibacterial corn starch film (57% reduction in bacterial count) with enhanced tensile strength (69%) by incorporating immobilized bacteriocin. Whisker shaped crystalline nanocellulose (CNC, length 71.2 ± 20.7 nm and width 27.8 ± 11.2 nm) was prepared from cotton linters by bio-mechanical process, having the degree of polymerization 250. Bacteriocins extracted from broth cultures of P. acidilactici and E. faecium were immobilized on the surface of CNC and used to reinforce the starch film. The biodegradability of reinforced films was affected due to the use of bacteriocin in fillers. Surface morphology and roughness of reinforced films were studied by SEM and AFM. In an ambient environment, the films incorporated with bacteriocin immobilized CNC stayed fresh for 28 days while that of bacteriocin alone had fungal degradation in 14 days. This supports the requirement of CNC immobilization for better stability of bacteriocin on storage.

Evaluation of autofluorescent property of hemoglobin-advanced glycation end product as a long-term glycemic index of diabetes.

Current methods for measuring long-term glycemia in patients with diabetes are HbA(1c) and advanced glycation end products (AGEs), which are estimated by phenyl boronate affinity chromatography and competitive enzyme-linked immunosorbent assay, respectively. In this study, we hypothesize that the intrinsic fluorescence property of hemoglobin-AGE (Hb-AGE) may be a simple, accurate, and therefore better index for long-term glycemic status due to its highly specific nature and longer half-life. To establish this contention, in vitro and in vivo experiments were carried out. The former was performed by incubating commercially available hemoglobin with 5 and 20 mmol/l glucose and the latter through experimentally induced (streptozotocin) diabetes in an animal model (male Wistar rats) to identify the new fluorophore formed due to the nonenzymatic glycosylation of hemoglobin. An adduct exhibiting fluorescence at 308/345 nm of excitation/emission wavelengths has been identified and its time-dependent formation established. Under in vitro conditions, the first appearance of the new fluorophore was noticed only after a period of 2 months, whereas under in vivo conditions, it increased significantly after 2 months of hyperglycemia. Consistent with the observations, studies on patients with type 2 diabetes demonstrated an elevated level of this new fluorescent adduct in patients with persisting high levels of plasma glucose for >2 months. Based on the results obtained, Hb-AGE appears to be an efficient fluorescence-based biosensing molecule for the long-term monitoring of glycemic control in diabetes.