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Introduction. Streptococcus pyogenes is a diverse virulent synthesis pathogen responsible for invasive systemic infections. Establishment of antibiotic resistance in the pathogen has produced a need for new antibiofilm agents to control the biofilm formation and reduce biofilm-associated resistance development. Aim. The present study investigates the in vitro antibiofilm activity of eucalyptol against S. pyogenes . Methodology. The antibiofilm potential of eucalyptol was assessed using a microdilution method and their biofilm inhibition efficacy was visualized by microscopic analysis. The biochemical assays were performed to assess the influence of eucalyptol on virulence productions. Real-time PCR analysis was performed to evaluate the expression profile of the virulence genes. Results. Eucalyptol showed significant antibiofilm potential in a dose-dependent manner without affecting bacterial growth. Eucalyptol at 300 µg ml−1 (biofilm inhibitory concentration) significantly inhibited the initial stage of biofilm formation in S. pyogenes . However, eucalyptol failed to diminish the mature biofilms of S. pyogenes at biofilm inhibitory concentration and it effectively reduced the biofilm formation on stainless steel, titanium, and silicone surfaces. The biochemical assay results revealed that eucalyptol greatly affects the cell-surface hydrophobicity, auto-aggregation, extracellular protease, haemolysis and hyaluronic acid synthesis. Further, the gene-expression analysis results showed significant downregulation of virulence gene expression upon eucalyptol treatment. Conclusion. The present study suggests that eucalyptol applies its antibiofilm assets by intruding the initial biofilm formation of S. pyogenes . Supplementary studies are needed to understand the mode of action involved in biofilm inhibition.

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Studies related to partial pressure of carbon dioxide (pCO 2) concentration linking with polychaete diversity in mangrove ecosystems are limited in time and space. Therefore, the present study was conducted during July 2017-June 2018 on a monthly interval and reported the concentration of pCO 2 coupled with physico-chemical parameters in relation to polychaetes diversity in Pichavaram mangroves ecosystem, southeast coast of India. Totally, 41 species were identified and the most dominant species were Prionospio cirrifera, P. cirrobranchiata, P. sexoculata, Prionospio sp. and Capitella capitata. Among the stations, higher polychaete diversity was found in marine zone compared to other zones. The correlation reflected a significant positive linear relationship between dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) and CO 2 versus pCO 2. The carbon species DIC, DOC, POC and pCO 2 concentration ranged from 1100.1 to 2053.3(µmol/kg), 165.7-1954.0(µmol/kg), 4.5-89.2(µmol/kg) and 184.7-3763.1(µatm), respectively. Further, the statistical analyses revealed that there was a strong correlation among carbon species with distribution of polychaete species in various zones of mangroves and thus indicating pivotal role in occurrence of polychaetes in mangroves.