Papers by LokaBharathi Ponnapakkam
Oceanologia, 2019
Phosphatase is an extracellular enzyme which releases inorganic phosphate (Pi) from dissolved org... more Phosphatase is an extracellular enzyme which releases inorganic phosphate (Pi) from dissolved organic phosphate and indirectly organic carbon as nutrients for aquatic communities. Here, we have examined spatiotemporal variation in total alkaline phosphatase activity (APA) over a short period off Trivandrum, SW India. Sampling was at 50 m water depth at 5, 15, 25 and 45 m for 5 consecutive days at 6 h intervals during post-monsoon season. Total APA and phosphatase producing bacteria (PPB) were estimated along with pertinent environmental parameters. APA increased with depth up to 3.98 mM P h À1 at 45 m. Increase in pigment concentration with depth is responsible for an increase in APA and Pi uptake. There is a marginal increase in APA towards 18-24 h suggesting feeding activities of secondary producers. On the whole, chlorophyll and phaeophytin were responsible for nearly 45 and 55% variation in APA (p < 0.01, p < 0.001, n = 16), respectively. Total bacterial count (TBC) was responsible for 32% (p < 0.05, n = 16) and total viable direct countsaerobic (TVCa) for 24% (p < 0.05, n = 16) APA variation. About 38% (p < 0.01, n = 20) variation of APA was linked to chlorophyll at noon and 22% (p < 0.001, n = 20) to PPB at dawn. Thus, it is possible that bacteria and chlorophyll/phytoplankton could be responsible for variation in APA, with the latter contribution greater than the former at noon. Such studies would help to profile the fertility of coastal waters in terms of bioavailable Pi. Laboratory experiments are underway to help us discern the extent of light-dependent contribution of chlorophyll/phytoplankton to APA and light independent participation of bacteria to the process.
A halotolerant, Gram positive, motile, rod was isolated from the salt pan sediments of Cavellosim... more A halotolerant, Gram positive, motile, rod was isolated from the salt pan sediments of Cavellosim, Salcette, Goa, India and screened for its antimicrobial potential. The strain showed an inhibitory effect specifically to Staphylococcus citreus. The isolate showed optimal growth as well as antibiotic production with 4% natural salt and could tolerate up to 6% salt. Dextrose and L-Tryptophan were found to be the best carbon and nitrogen sources for optimum antibiotic production. Based on morphological, biochemical, 16S rDNA sequencing and phylogenetic analysis, the strain was identified as B. marismortui.
interested in studying about marine microbes and their role in various bigeochemical cycles in th... more interested in studying about marine microbes and their role in various bigeochemical cycles in the marine environment. Dimethyl sulphide (DMS) was reported in oceanic waters by Lovelock et al., (1972). Its precursor Dimethyl sulfoniopropionate (DMSP) is ubiquitous in the euphotic zone especially in regions dominated by phytoplankton. The biogeochemical importance of DMSP is based on its bacterial (Wolfe et al., 1999) or algal mediated (Steinke et al., 2002) enzymatic cleavage to acrylic acid and dimethyl sulphide (DMS). Dissolved DMSP can satisfy 1-15 % of the total bacterial carbon and virtually all of the bacterial sulfur demand (Kiene et al., 2000; Simo et al., 2002). Bacteria play an important
Marine Drugs, 2010
The subject of this review is the biodiversity of marine sponges and associated microbes which ha... more The subject of this review is the biodiversity of marine sponges and associated microbes which have been reported to produce therapeutically important compounds, along with the contextual information on their geographic distribution. Class Demospongiae and the orders Halichondrida, Poecilosclerida and Dictyoceratida are the richest sources of these compounds. Among the microbial associates, members of the bacterial phylum Actinobacteria and fungal division Ascomycota have been identified to be the dominant producers of therapeutics. Though the number of bacterial associates outnumber the fungal associates, the documented potential of fungi to produce clinically active compounds is currently more important than that of bacteria. Interestingly, production of a few identical compounds by entirely different host-microbial associations has been detected in both terrestrial and marine environments. In the Demospongiae, microbial association is highly specific and so to the production of compounds. Besides, persistent production of bioactive compounds has also been encountered in highly specific host-symbiont associations. Though spatial and temporal variations are known to have a marked effect on the quality and quantity of bioactive compounds, only a few studies have covered these dimensions. The need to augment production of these compounds through tissue culture and mariculture has also been stressed. The reviewed database of these compounds is available at www.niobioinformatics.in/drug.php.
Marine Georesources & Geotechnology, 2005
Abstract: It is anticipated that in the case of mining of marine minerals, sea floor sediments wi... more Abstract: It is anticipated that in the case of mining of marine minerals, sea floor sediments will be brought up along with the mineral ores and discharged on the surface. These nutrient rich sediments would create a set of different physicochemical conditions at the point of ...
Journal of Sea Research, 2015
Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during sum... more Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May-September). We hypothesise that there could be a shift in environmental parameters along with changes in network of interactions between bacteria, phytoplankton, and zooplankton in upwelling and non-upwelling regions. During cruise # 267 on FORV Sagar Sampada, water samples were analysed for environmental and biological parameters from two transects, one upwelling region off Trivandrum (TVM) (8°26′N,76°20′E-8°30′N,76°50′E), and the other non-upwelling region off Calicut (CLT) (11°11′N,75°30′E-11°14′N,74°54′E), about 230 nmi to the north. Meteorological, hydrological, and nutrient profiles confirmed upwelling off TVM. Bacteria, phytoplankton and zooplankton significantly responded. Primary and bacterial productivity enhanced together with increase in the percentage of viable bacteria (TVC). Pearson's correlation analysis pointed out the differences in bacterial interactions with other trophic levels at both transects. TVC played a prominent role in trophic interactions off TVM by depending on phytoplankton for substrate (r=0.754). This contrasted with CLT where total counts (TC) played an important role. However, most interrelationships were less pronounced. Principal component analysis (PCA) confirmed the correlation analysis and further showed that the factor loadings of the biotic and abiotic parameters differed in strength and direction in the two regions. More importantly, the processes of mineralization by bacteria and uptake by phytoplankton are obviously more coupled off TVM as evidenced by the clustering of the related parameters in the PCA biplot. Canonical correspondence analysis also complements these findings and demonstrated that the abiotic factors influenced phytoplankton and bacteria, differently -inversely and definite at TVM and more diverse and varied at CLT. The impact on the trophic interrelationships is evident by the close association between all the variables in upwelling waters. Besides, bacteria may represent a more stable element in the food web, TVC for upwelling region and TC for non-upwelling region.
Environmental science and pollution research international, Jan 25, 2015
The coastal waters of Goa and Ratnagiri lying on the West coast of India are influenced by terres... more The coastal waters of Goa and Ratnagiri lying on the West coast of India are influenced by terrestrial influx. However, Goa is influenced anthropogenically by iron-ore mining, while Ratnagiri is influenced by deposition of heavy minerals containing iron brought from the hinterlands. We hypothesize that there could be a shift in biological response along with changes in network of interactions between environmental and biological variables in these mining and non-mining impacted regions, lying 160 nmi apart. Biological and environmental parameters were analyzed during pre-monsoon season. Except silicates, the measured parameters were higher at Goa and related significantly, suggesting bacteria centric, detritus-driven region. At Ratnagiri, phytoplankton biomass related positively with silicate suggesting a region dominated by primary producers. This dominance perhaps got reflected as a higher tertiary yield. Thus, even though the regions are geographically proximate, the different bi...
... 1975)- Although some information is available on the isolation and enumeration of mic;-0-orga... more ... 1975)- Although some information is available on the isolation and enumeration of mic;-0-organisms of thetemperate sandy beaches (Litchfield, Rake, Zindulis, Watanabe and Stein, 1975; Rheinheimer, I977; Boeye, Wayenbergh and Aerts, 1975), little is known about the ...
... 3, pp 79-92 ABUNDANCE, VIABILITY AND CULTURABILITY OF ANTARCTIC BACTERIA PALoka Bharathi, M J... more ... 3, pp 79-92 ABUNDANCE, VIABILITY AND CULTURABILITY OF ANTARCTIC BACTERIA PALoka Bharathi, M JBD De Souza, S ... As the tubes were incubated under low ambient temperatures of 8-12°C, the period of incubation was Page 4. 82 PA Loka Bharathi etat. 12tX>'E Fig. ...
... 7: 9|? I02. Page 7. Hererorrophic hacreria and lnochcnziml ncri&#x27;rin&#x27;es 81 E... more ... 7: 9|? I02. Page 7. Hererorrophic hacreria and lnochcnziml ncri&#x27;rin&#x27;es 81 Ezura; Y., K. D_aiku, K. Tajima, T-Kimura and M-Sakai, 1974. ... I968 Bacterial life in deep sea. Bulletin of Misaki Marine .Bl:Jl()gl(&#x27;(ll lr1.\&quot;l-lure, Kyoto University, I2: 77-95-ZoBeIl, CF., 1972. ...
A profiling underwater radiometer was used for the first time in the waters around Indian Antarct... more A profiling underwater radiometer was used for the first time in the waters around Indian Antarctic Station (70°46&amp;#39;S &amp;amp;amp; 1 l°44&amp;#39;E) in the summer of 1994. The profiles include natural fluorescence (upwelled radiance at 683 nm), scalar irradiance (photosynthetically active radiation (PAR), computed primary production (pp), diffuse attenuation coefficient, and UVB (308 and 320 nm) and UVA (340 and 380
... The infor-mation available about these forms in Indian waters has been restricted to es-tuari... more ... The infor-mation available about these forms in Indian waters has been restricted to es-tuarine ecosystems (Loka Bharathi and Chandramohan, 1985 ... were collected from three different areas: near shore, lagoons and mud banks during cruise 147 of RV GAVESHINI (NIO India). ...
... After Pillai, the next person in the country who has developed interest on corals and coral r... more ... After Pillai, the next person in the country who has developed interest on corals and coral reefs is the author of the present article Dr. MVM Wafar. ... Indoor Air Quality - an Emerging Environmental Challenge Vinita Katiyar and M. Khare 1 2 4 5 7 10 11 Page 2. ...
Page 107. Chapter 14 7 Marine Microbiology A Glimpse of the Strides in the Indian and the Global ... more Page 107. Chapter 14 7 Marine Microbiology A Glimpse of the Strides in the Indian and the Global Arena PA. Loka Bharathi, Shanta Nair and D. Chandramohan 1. INTRODUCTION Marine microbiology is the realm where marine science and microbiology meet. ...
... Received 1 April 2005; revised accepted 3 December 2005 984 Marine and estuarine methylotroph... more ... Received 1 April 2005; revised accepted 3 December 2005 984 Marine and estuarine methylotrophs: their abundance, activity and identity Daphne Faria and PA Loka Bharathi* Biological Oceanography Division, National Institute of ... (e-mail: loka@nio.org) CURRENT ...
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Papers by LokaBharathi Ponnapakkam