Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Recruitment in the sea: bacterial genes required for inducing larval settlement in a polychaete worm

Metamorphically competent larvae of the marine tubeworm Hydroides elegans can be induced to metamorphose by biofilms of the bacterium Pseudoalteromonas luteoviolacea strain HI1. Mutational analysis was used to identify four genes that are necessary for metamorphic induction and encode functions that may be related to cell adhesion and bacterial secretion systems. No major differences in biofilm characteristics, such as biofilm cell density, thickness, biomass and EPS biomass, were seen between biofilms composed of P. luteoviolacea (HI1) and mutants lacking one of the four genes. The analysis indicates that factors other than those relating to physical characteristics of biofilms are critical to the inductive capacity of P. luteoviolacea (HI1), and that essential inductive molecular components are missing in the non-inductive deletion-mutant strains

Properties of an alkali-thermo stable xylanase from Geobacillus thermodenitrificans A333 and applicability in xylooligosaccharides generation

An extracellular thermo-alkali-stable and cellulase-free xylanase from Geobacillus thermodenitrificans A333 was purified to homogeneity by ion exchange and size exclusion chromatography. Its molecular mass was 44 kDa as estimated in native and denaturing conditions by gel filtration and SDS-PAGE analysis, respectively. The xylanase (GtXyn) exhibited maximum activity at 70 °C and pH 7.5. It was stable over broad ranges of temperature and pH retaining 88 % of activity at 60 °C and up to 97 % in the pH range 7.5–10.0 after 24 h. Moreover, the enzyme was active up to 3.0 M sodium chloride concentration, exhibiting at that value 70 % residual activity after 1 h. The presence of other metal ions did not affect the activity with the sole exceptions of K+ that showed a stimulating effect, and Fe2+, Co2+ and Hg2+, which inhibited the enzyme. The xylanase was activated by non-ionic surfactants and was stable in organic solvents remaining fully active over 24 h of incubation in 40 % ethanol at 25 °C. Furthermore, the enzyme was resistant to most of the neutral and alkaline proteases tested. The enzyme was active only on xylan, showing no marked preference towards xylans from different origins. The hydrolysis of beechwood xylan and agriculture-based biomass materials yielded xylooligosaccharides with a polymerization degree ranging from 2 to 6 units and xylobiose and xylotriose as main products. These properties indicate G. thermodenitrificans A333 xylanase as a promising candidate for several biotechnological applications, such as xylooligosaccharides preparation

Role of conspecific cues and sugars in the settlement of cyprids of the barnacle, Balanus amphitrite

Gregarious settlement in barnacle is attributed to the settlement-inducing protein complex of cuticular glycoprotein, arthropodin. In this study, we characterized arthropodin protein complex (APC) from crude protein extracts of whole barnacle (AE), and also from soft body (SbE) and shell (ShE). The settlement of cyprids exposed to surfaces coated with different crude protein extracts and APC components was evaluated. In the natural environment, larvae are also exposed to different dissolved sugars. Therefore, the cyprids were tagged with different sugars and exposed to AE, SbE and ShE in order to elucidate their specific role in determining the way barnacle cyprids identify conspecifics. A previously undescribed 66-kDa subunit was observed in shell and soft body APC, and a 98-kDa subunit was observed in shell APC. Both the subunits were shown to inhibit settlement when alone but promoted settlement in combination (ShE), suggesting that these proteins interact in a coordinated manner. The crude adult extract (AE) facilitated higher settlement compared with shell or soft body extract. However, when cyprids were tagged with different sugars and exposed to the surfaces coated with different crude protein extracts, settlement response differed and was jointly determined by the type and concentration of sugars. Such interactions could play an important role in nature as larvae encounter surfaces covered with different glycoproteins and also experience different dissolved cues

Factors regulating the production of different inducers in Pseudomonas aeruginosa with reference to larval metamorphosis in Balanus amphitrite

Gregarious settlement in barnacles has been related to the settlement-inducing compounds from adult conspecifics, bacteria in the biofilms, and their interaction. Elucidation of larval settlement cues from these sources is limited. The effectiveness of larval settlement cues under different environmental conditions (salinity, temperature) needs evaluation. Pseudomonas aeruginosa, a bacterium isolated from the shell surface of Balanus amphitrite Darwin, was used as a candidate. The influence of bacterial film, culture supernatant and its molecular-weight fractions, and bacterial extract was investigated along with the conspecific adult extract (AE). The influence of culture supernatants and exopolysaccharides obtained from the bacterium cultivated in different nutrient media, effectiveness of leachants and adsorbed (surface-bound) compounds on the metamorphosis of cyprids of B. amphitrite was also assessed. The influence of P. aeruginosa on cyprid metamorphosis varied with salinity and temperature. The differences were not significant as the film and the cyprids aged. When the bacterial film was examined in the presence of an active substance (agonist) such as AE, metamorphosis was facilitated, suggesting the role of competitive antagonism in cue perception. The higher molecular-weight fraction of the bacterial-culture supernatant was inductive at higher salinity. Conversely, the lower molecular-weight fraction of the culture supernatant showed maximum inhibition when the adsorbed (surface-bound) compounds were assessed along with the leachants. Bacterial extract showed the presence of ketonic compounds, and its influence differed with salinity. The inhibitory effect of the extract was nullified in the presence of AE. When the extract was examined in the presence of leachants, a 2-fold increase in the metamorphosis rates was evident where only surface-bound components were inhibitory. Fourier transformed infrared spectroscopy analysis revealed that bacteria grown in different nutrient media yielded culture supernatants with different chemical composition, thus altering their ability to induce metamorphosis of cyprids. Maximum inducement was provoked by the culture supernatant obtained from semi-solid culture, and this positive effect was protein concentration dependent. The exopolysaccharides obtained from bacteria grown in basal salt solution facilitated metamorphosis similar to that of the bacterial film and AE. The response of the cyprids to bacteria and its products seems to be regulated by both contact chemoreception and olfaction, depending on the properties of the settlement-inducing compounds. The need to characterize and distinguish the receptors, which act via different signaling systems on a particular settlement cue, may be a step ahead to resolve the complexities of invertebrate larval recruitment

Thraustochytrid protists as a component of marine microbial films

Although ubiquitous in the marine environment, the presence and importance of thraustochytrid fungoid protists in primary film formation of freshly immersed surfaces in the sea have not been investigated. We isolated thraustochytrids from surfaces of glass, aluminium, mild steel and fibre glass panels immersed in sea water for 1 to 4 d, but not from those of copper and cupro-nickel. Microscopic examination of the primary film on glass surfaces revealed the presence of thraustochytrids. Thraustochytrids grew to varying population densities on surfaces of glass, aluminium and fibre glass in the laboratory. Scanning electron microscopy of the growth of Ulkenia profunda Gaertner, isolated from the primary film, on surfaces of glass and aluminium suggested that cells of the thraustochytrid attached directly to the surfaces, without producing copious extracellular polysaccharides. The presence of ectoplasmic net elements was not a prerequisite for attachment of cells to surfaces. Cell surface hydrophobicity of the thraustochytrid, as estimated by the MATH assay, might play an important role in adhesion. The presence of thraustochytrid cells on a polystyrene surface markedly induced settlement of barnacle larvae (Balanus amphitrite), as compared to barnacle extract and a control

Influence of bacterial exopolymers and the adult extract of Balanus amphitrite and Cthamalus sp. on cyprid metamorphosis of Balanus amphitrite

Settlement of barnacle, a major fouling organism is believed to be controlled to a great extent by substratum characteristics such as, presence of conspecific adults or "gregariousness" inducing factors. Exopolymers secreted by bacteria can also play a major role in the recruitment of larvae of fouling organisms, probably by providing inducing/inhibitory chemical cues. In this experiment, the influence of the extract of adult Balanus amphitrite and the expolymers of the bacteria colonising Balanus amphitrite in nature on the cyprid metamorphosis of B. amphitrite has been examined. The experiments were carried out in polystyrene multiwells. A similar set of experiments was also repeated with the extract of Cthamalus sp. which co-exists in the intertidal zone along with B. amphitrite. The results obtained indicate that the addition of exopolymers as well as adult extract promoted settlement of cyprids. The degree of inducement varied with various combinations of exopolymers of different bacterial strains with or without adult extract of both the species

Fouling diatom community with reference to substratum variability in tropical marine environment

Diatoms are the earliest autotrophic colonizers and are responsible for the major input of energy in the form of reduced carbon to the surfce. However, information regarding the population structure of diatoms in theearly phases of fouling is very limited. In the present study, enumeration of fouling diatom population was carried out by exposing different types of substrata for four consecutive days at the sub-surface level. The study was carried out at Dona Paula bay located at the mouth of the Zuari estuary along the west cost of India. Quantification of the attached organisms from different substrata and from the surrounding environment was carried out microscopically and by the chlorophyll a estimation. navicula sp. was the most abundant form encountered. The paper deals with the qualitative and quantitative aspects of diatom colonization, their community structure, and correlation between the prevailing diatom population in the environment and that in the fouling community