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Microfouling development on artificial substrates deployed in the central Red Sea

Balqadi A. A., Salama A. J., Satheesh S.

Oceanologia

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2018

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No. 60 (2)

219--231

EN

Microfouling is the initial step in the growth of biofouling on hard substrata submerged in marine waters. In this study, microfouling development on nylon nets submerged in the central Red Sea coast of Saudi Arabia was analyzed during the winter and summer seasons for a period of 5 days each. The results showed a well-established biofilm community on nylon nets submerged for 24 h, with bacteria and diatoms being the primary colonizers. Protein was the major organic component of the biofilm that developed on the nylon nets during the winter and summer seasons. Navicula spp., Nitzschia spp., Cylindrotheca spp., and Pluerosigma spp. were the dominant diatom species settled on the nylon nets. Pseudoalteromonas shioyasakiensis, Planomicrobium sp., Vibrio harveyi and Pseudoalteromonas rubra were the dominant bacteria isolated from the nylon nets. While the abundance of bacteria showed a positive correlation with the nutrient concentration of the biofilm during both winter and summer seasons, diatom density exhibited a significant positive relationship with the biofilm nutrients during the winter season only. The results also revealed significant seasonal variations in the abundance of microfouling organisms and accumulation of nutrients on nylon nets.

2

Antibiofilm and antifouling activities of extracellular polymeric substances isolated from the bacteria associated with marine gastropod Turbo sp.

Viju N., Satheesh S., Punitha S. M. J.

Oceanological and Hydrobiological Studies

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2016

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Vol. 45, No. 1

11--19

EN

The extracellular polymeric substances (EPS) produced by the bacteria associated with the gastropod Turbo sp. were isolated and screened for antibacterial activity against biofilm-forming bacteria. EPS of five out of 13 strains showed inhibitory activities in the antibacterial assay. Furthermore, the antibiofilm and antifouling activity of the most active EPS isolated from the strain KT1 was studied using various in vitro and in vivo bioassays. Results revealed that EPS significantly inhibited the growth and biofilm formation of bacteria. Furthermore, the antifouling coating developed with bacterial EPS considerably reduced the recruitment of fouling organisms on coated surfaces submerged in the seawater. The functional groups present in EPS, characterized by strong activity,were analyzed using FT-IR and the spectrum showed the presence of alcohol, amines, carboxylic acid and esters. The bacterium responsible for the production of bioactive EPS was identified as Pseudomonas aeruginosa, using the 16S rRNA gene. Since the findings of this study revealed the antibiofilm and antifouling activities of EPS, further long term field tests and characterization of the bioactive compound of the EPS could lead to the development of eco-friendly antifouling coating.

3

Larval development and settlement of the barnacle Amphibalanus amphitrite from the Red Sea : Influence of the nauplii hatching season

Al-Aidaroos A.M., Satheesh S.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 2

170--177

EN

Barnacle Amphibalanus amphitrite adults were collected from the Jeddah coast of the Red Sea during different seasons. The nauplii released by adults in autumn, winter, spring and summer were reared under laboratory conditions to know the larval development duration and settlement in relation to the hatching season. The nauplii reared during winter (11 days) and autumn (13 days) took longer to reach the cypris stage compared to nauplii reared in summer (6 days) and spring (7 days). The most successful settlement of larvae was observed in spring and summer and the least successful — in winter. The observations of gonads showed that summer and spring are the active breeding season for A. amphitrite in the Red Sea. The results of this study indicated that the nauplii hatching season plays a significant role in the larval development and settlement of barnacles in the Red Sea.

4

Exposure to chlorine affects the extracellular polymeric substance production and cell surface hydrophobicity in biofilm bacteria

Rathi R., Satheesh S.

Oceanological and Hydrobiological Studies

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2012

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Vol. 41, No. 4

17-24

EN

Chlorination is a common antifouling method adopted by industrial units to minimize the fouling growth on cooling systems. In the present study, the effect of sodium hypochlorite on extracellular polymeric substance (EPS) production, hydrophobicity, cell adhesion and viability of marine bacteria involved in biofilm formation were assessed in laboratory condition. Two bacterial strains, tentatively identified as Alteromonas sp. and Pseudomonas sp. isolated from the surface of seaweeds were used as test organisms for the present study. The bacterial cultures were treated with sodium hypochlorite at 25% of the minimum inhibitory concentration. Results showed considerable variation in the production of EPS, viable counts, hydrophobicity and adhesion ability of bacteria treated with sodium hypochlorite. In general, the present study indicated that chlorination affects some important characteristics involved in the biofilm formation and thereby reduces the adhesion rate on surfaces.

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Biofilm development on acrylic coupons during the initial 24 hour period of submersion in a tropical coastal environment

Satheesh S., Wesley S.G.

Oceanological and Hydrobiological Studies

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2010

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Vol. 39, No.1

27-38

EN

The sequence of biofilm formation on a hard surface during the first 24 hours in a coastal environment was studied by suspending acrylic coupons. Adsorption of carbohydrates, proteins, calcium, magnesium, nitrite, nitrate and phosphate were monitored along with microbes. The results showed that carbohydrate, protein, nitrite and nitrate were adsorbed on the coupons within an hour of exposure. Carbohydrates showed a maximum value of 0.28 mg cm-2 after 24 hours and protein concentration reached up to a maximum of 0.41 mg cm-2. Adsorption of calcium and magnesium was observed after three hours. Settlement of bacteria was also observed on coupons within an hour and diatoms were observed after 15 hours. Diatoms such as Navicula and Nitzschia were the dominant colonizers during the early stages of biofilm development.