Biology subjects

Shukla, S. K.

Publications and source records attributed to Shukla, S. K..

3 recordsLinked to original sources

bioRxiv2017

The first recorded incidence of Deinococcus radiodurans R1 biofilm formation and its implications in heavy metals bioremediation

Radiation tolerant Deinococcus radiodurans R1 is reported to be a potential bacterium for the treatment of low level active wastes. So far there are no reports on the biofilm producing capability of D. radiodurans and heavy metal biosorption. In this study, it was observed that a recombinant D. radiodurans strain with a plasmid harbouring gfp and kanR has formed significant biofilm (~10 m thick). Analysis of biofilm matrix components produced by D. radiodurans showed that the matrix consisted primarily of proteins and carbohydrates with a little amount of extracellular DNA (eDNA). Further, studies showed that D. radiodurans biofilm formation was enhanced at higher concentrations (up to 25 mM) of Ca2+. Further studies on D. radiodurans biofilm showed that Ca2+ enhanced significant biosorption of the heavy metals (Co, Ni). In the presence of 25 mM Ca2+, the D. radiodurans (Kanr) biofilm showed 35% and 25% removal of Co2+ and Ni2+ respectively. While in the absence of Ca2+, D. radiodurans biofilm showed relatively low biosorption of Co (7%) and Ni (3%). Ca2+ also significantly enhanced exopolysaccharide (EPS) production in the biofilm matrix. This infers that EPS could have mediated the heavy metal biosorption. This study signifies the potential use of D. radiodurans biofilm in the remediation of radioactive waste components.\n\nSignificance and Impact of this StudyThis is the first ever recorded study on the Deinococcus radiodurans R1 biofilm. This organism, being the most radioresistant micro-organism ever known, has always been speculated as a potential bacterium to develop a bioremediation process for radioactive heavy metal contaminants. However, the lack of biofilm forming capability proved to be a bottleneck in developing such technology. This study records the first incidence of biofilm formation in a recombinant D. radiodurans, serendipitously, and also discusses its implications in removal of heavy-metals, such as Co and Ni.

microbiology↗

bioRxiv2017

Staphylococcus aureus Biofilm Removal by Targeting Biofilm-Associated Extracellular Proteins

AimAmong cell surface proteins, biofilm-associated protein promotes biofilm development in Staphylococcus aureus strains. Aim of this study was to investigate proteinase-mediated biofilm dispersion in different isolates of S. aureus.\n\nMethods and ResultsMicrotitre plate based biofilm assay showed that 2 g/mL proteinase K significantly inhibited biofilm development in bap-positive S. aureus V329 as well as other S. aureus strains, i.e. SA7, SA10, SA33, SA352 and but not in bap-mutant M556 and SA392 (a weak biofilm producing strain). However, proteinase K treatment on S. aureus planktonic cells showed that there was no inhibition of planktonic growth at any concentration of proteinase K when tested up to 32 g/mL. This observation ruled out the possibility of S. aureus biofilm inhibition by altering the cell viability. Proteinase K treatment upon 24 h old preformed biofilms showed an enhanced dispersion of bap-positive V329 and SA7, SA10, SA33 and SA352 biofilms, however, proteinase K did not affect the bap-mutant S. aureus M556 and SA392 biofilms. Biofilm compositions study before and after proteinase K treatment indicated that Bap might also be involved in eDNA retention in the biofilm matrix that aid in biofilm stability. When proteinase K was used in combination with antibiotics, a synergistic effect in antibiotic efficacy was observed against all biofilm forming S. aureus strains.\n\nConclusionProteinase K inhibited biofilms growth in S. aureus bovine mastitis isolates but did not affect their planktonic growth. An enhanced dispersion of preformed S. aureus biofilms was observed upon proteinase K treatment. Proteinase K treatment with antibiotics showed a synergistic effect against S. aureus biofilms.\n\nSignificance of the studyThe study suggests that dispersing S. aureus by protease can be of use while devising strategies against S. aureus biofilms. Proteinase K treatment has a wider scope for control of S. aureus biofilms.

microbiology↗

bioRxiv2017

An Improved Crystal Violet Assay for Biofilm Quantification in 96-Well Microtitre Plate

Microplates are essential tools for biofilm research since it allows high throughput screening of biofilm forming strains or in the assay of anti-biofilm drugs. However, 96 well microtitre plate based assays share the issue of \"edge effect\". The primary cause of the \"edge effect\" phenomenon is evaporation. As edge effect causes a significant increase in plate rejection rate by introducing experimental error, we improvised the classical crystal violet assay to reduce water loss from the peripheral wells. The improvised method showed a significant reduction in edge effect and minimised error in crystal violet assay

microbiology↗