Kandasamy Kathiresan

This work studied the antioxidant and anti-breast cancer properties of hyaluronidase, extracted from a potential marine strain, Staphylococcus aureus (CASMTK1), isolated from Parangipettai coastal waters in southeast coast of India. The Staphylococcal enzyme production was tested under different carbon and nitrogen sources; and recorded the maximum production when the microbial strain was cultured with starch as the carbon source and ammonium sulphate as the inorganic nitrogen source with the enzyme production of 92.5 U/mL and 95.0 U/mL, respectively. The hyaluronidase enzyme production was also tested in different pH and temperature; and recorded the maximum yield of 102.5 U/mL in pH 5 and that of 95.5 U/mL in 45 °C. The partially purified enzyme was subjected to FTIR and FT Raman technique and found the presence of the amide- I and II, Carboxyl, N-H bending, C-H stretching and α-helices and β-sheet proteins between wave number 1500–1700 cm⁻¹. The partially purified enzyme also exhibited strong antioxidant and in-vitro breast cancer properties. The enzyme showed the highest hydroxyl radical scavenging activity of 79% at the 50 µg/mL concentration, and this activity increased in a dose-dependent manner. The enzyme inhibited proliferation of the breast cancer cell line of MCF-7, and it caused 100% cell death at the concentration of 80 µg/mL. The enzyme generated capacity of producing free radicles that damage the cancer cells, and this effect was very nearer to the standard drug, paclitaxel. The enzyme damaged the cancer cells and induced apoptosis in 78% of cancer cells as evident by condensed or fragmented chromatin at 40 µg/mL. Further purification of the enzyme, analysis of its molecular aspects, and elucidation of exact mechanisms of its biological activities will throw new light on the utility of staphylococcal hyaluronidase in anticancer chemotherapy.

Burrowing crabs are considered to be ecosystem engineers, playing a vital role in mangrove ecosystems through bio-geochemical transformation. This process depends on the size and shape of burrows. The present study analyzes the architecture of burrows constructed by crabs in a restored mangrove habitat. Fourteen crab species were found to construct burrows of 13 different shapes, with a predominance of I-, J-, and L-shapes. Sesarmids were larger in size than fiddlers, and made burrows with wider openings mostly in the Rhizophora zone. Fiddlers constructed complex burrows with a vertical position, and made longer and deeper burrows in contrast to sesarmids, which formed simple burrows with a horizontal position, digging shorter and shallower burrows in Avicennia or open zones. The sesarmids had smaller burrows without branching in mangrove zones, whereas the fiddlers had larger burrows with or without branching in open and Avicennia zones. The burrows of fiddler crabs, especially Austruca occidentalis and A. annulipes, had separate openings and passages for exit and entry as an adaptation against predators. The present work identified Austruca occidentalis and A. annulipes as the most potent bioturbating crab species in restored mangrove habitats due to their efficiency in soil excavation and formation of large-sized burrows.

Burrowing crabs are considered to be the ecosystem engineers in mangrove ecosystems because they have impact on the ecosystem functioning through bio-geochemical transformations. This process depends on the size and shape of burrows. The present study analysed architecture of burrows, constructed by crabs in a restored mangrove habitat. Fourteen crab species were found to construct the burrows of 13 different shapes with predominance of ‘I’,’J’,’L’. The burrow shape was diverse in Metopograpsus messor, followed by Austruca occidentalis, Gelasimus vocans, and A. annulipes. The burrow structural complexity was higher during summer in Avicennia or open zone. Sesarmids were larger in size than fiddlers, making the burrows of wider opening. Fiddlers were relatively smaller in size and they constructed complex burrows at vertical position, making longer and deeper burrows, in contrast to sesarmids, which formed simple burrows at horizontal position, digging shorter and shallower burrows. The sesarmids have smaller burrows without branching in mangrove zones, whereas the fiddler crabs (except Austruca variegata) have larger burrows with or without branching in open and Avicennia zones. The fiddler crabs especially Austruca occidentalis and A.annulipes have separate openings and passage for exit and entry as an adaptation against predators. The present work identified Austruca occidentalis and A. annulipes as the most potent bio-turbating crab species for restored mangrove habitats due to their efficiency in soil excavation and large sized burrows.

This work studied the antioxidant and anti-colorectal cancer properties of a potential strain of thraustochytrids, Schizochytrium sp. (SMKK1), isolated from mangrove leaf litter. The biomass was extracted with methanol and screened for antioxidant activity using six different assays. The extract exhibited the highest total antioxidant activity (87.37 ± 1.22%) and the lowest nitric oxide radical (75.12 ± 2.22%), and the activity increased with the concentration of the extract. The methanolic extract was further tested for in vitro cytotoxicity on the colon cancer cell line (HT29). The extract was also analyzed for polyunsaturated fatty acids using GC-MS. The five predominant HTVS-based compounds, viz., arachidonic acid, linolenic acid (alpha-linolenic acid and gamma-linolenic acid), eicosapentaenoic acid, and docosahexaenoic acid, were identified in the extract, and these were tested against the colon cancer protein IGF binding (IGF-1) using the in silico docking method. The results revealed that all the five compounds were capable of destroying the colon oncoprotein responsible for anti-colon carcinogen, based on activation energy and also good hydrogen bond interaction against IGF binding proteins. Of the compounds, docosahexaenoic acid was the most effective, having a docking score of −10.8 Kcal/mol. All the five fatty acids passed the ADMET test and were hence accepted for further clinical trials towards the development of anticancer drugs.

Differences in grain size, total organic carbon (OC), total nitrogen (TN), OC/TN ratios, and stable isotope (δ¹³C and δ¹⁵N) were assessed in sediments from areas covered by mangrove and saltmarsh vegetation within Pichavaram estuary (Southeast India). The mean percentage contents of silt and clays (70 vs. 19%), OC (5.7 vs. 2.0%), and TN (0.39 vs. 0.14%) were consistently higher in the mangrove as compared to those observed in the saltmarsh tidal zone. These differences may obey the higher deposition and retention of fine particles in the presence of a mangrove root system that may facilitate the accumulation and preservation of organic matter within these sedimentary systems. Further, higher OC and TN contents were associated to higher terrestrial or mangrove-derived organic matter contribution with lighter δ¹³C signatures (−26.0‰) in both sedimentary tidal zones, whereas lower OC and TN contents were associated to heavier δ¹³C signatures. This study is in agreement with previous studies which indicate that the presence of wetland vegetation may increase the carbon and nutrient storage capacity within estuarine ecosystems, highly relevant information for the establishment of further conservation strategies for blue carbon ecosystems at global scales.

This work deals with the identification of a predominant thraustochytrid strain, the optimization of culture conditions, the synthesis of nanoparticles, and the evaluation of antioxidant and antimicrobial activities in biomass extracts and nanoparticles. Thraustochytrium kinnei was identified as a predominant strain from decomposing mangrove leaves, and its culture conditions were optimized for maximum biomass production of 13.53 g·L⁻¹, with total lipids of 41.33% and DHA of 39.16% of total fatty acids. Furthermore, the strain was shown to synthesize gold and silver nanoparticles in the size ranges of 10–85 nm and 5–90 nm, respectively. Silver nanoparticles exhibited higher total antioxidant and DPPH activities than gold nanoparticles and methanol extract of the strain. The silver nanoparticles showed higher antimicrobial activity than gold nanoparticles and petroleum ether extract of the strain. Thus, Thraustochytrium kinnei is proven to be promising for synthesis of silver nanoparticles with high antioxidant and antimicrobial activity.

Based on intensive literature survey, thorough herbaria consultations, and extensive field surveys (2012–2017) along the coast of Tamil Nadu, besides consulting experts and botanists to resolve the typification and nomenclatural issues, the discovery, nomenclature, lectotype, distribution, and the present status of the coastal stenoendemic legume, Vachellia bolei (syn. Acacia bolei), in southern India, is discussed here in detail. Clarification regarding the Lectotype of the taxon is made and the extinction of the species is reported.

Xylocarpus granatum J. Koenig is one of the most widespread core component species of mangrove forests in the Indo-West Pacific (IWP) region, and as such is suitable for examining how genetic structure is generated across spatiotemporal scales. We evaluated the genetic structure of this species using maternally inherited chloroplast (cp) and bi-parentally inherited nuclear DNA markers, with samples collected across the species range. Both cp and nuclear DNA showed generally similar patterns, revealing three genetic groups in the Indian Ocean, South China Sea (with Palau), and Oceania, respectively. The genetic diversity of the Oceania group was significantly lower, and the level of population differentiation within the Oceania group was significantly higher, than in the South China Sea group. These results revealed that in addition to the Malay Peninsula—a common land barrier for mangroves—there is a genetic barrier in an oceanic region of the West Pacific that prevents gene flow among populations. Moreover, demographic inference suggested that these patterns were generated in relation to sea level changes during the last glacial period and the emergence of Sahul Shelf which lied northwest of Australia. We propose that the three genetic groups should be considered independent conservation units, and that the Oceania group has a higher conservation priority.