Sterile Seawater Research Articles

Bioaccumulation and persistence of faecal bacterial and viral indicators in Mytilus edulis and Crassostrea gigas.

This study investigated the response of two shellfish species - mussels (Mytilus edulis) and oysters (Crassostrea gigas) to microbial contamination in order to gain a better understanding of the bioaccumulation and persistence of microorganisms under controlled conditions. M. edulis and C. gigas were placed in sterile laboratory-prepared artificial seawater and initial tests were carried out to ensure both faecal indicator bacteria (FIB) and bacteriophages were below detection limits. FIB and phages were isolated, purified and dosed into experimental tanks containing the shellfish species. The GB124 phages were bioaccumulated to the highest concentration in M. edulis (1.88Log10) and C. gigas (1.27Log10) after 24h. Somatic coliphages were bioaccumulated to the highest concentration in both M. edulis (4.84log10) and C. gigas (1.73log10) after 48h. F-RNA phages were bioaccumulated to the highest concentration in M. edulis (3.51log10) after 6h but were below detection limit in C. gigas throughout the exposure period. Escherichia coli, faecal coliforms and intestinal enterococci were bioaccumulated to the highest concentrations in M. edulis (5.05log10, 5.06log10 and 3.98log10, respectively) after 48h. In C. gigas, E. coli reached a maximum concentration (5.47log10) after 6h, faecal coliforms (5.19log10) after 12h and intestinal enterococci (3.23log10) after 24h.M. edulis bioaccumulated phages to a greater extent than the faecal bacteria, and in both shellfish species, faecal bacteria persisted for longer periods over 48h than the phages. This study highlights significant variation in the levels and rate of accumulation and persistence with respect to both shellfish species and the indicators used to assess risk. The results suggest that phage-based indicators could help elucidate risks to human health associated with pathogenic organisms.

Oil Spill Biodegradation by Bacteria Isolated from Jakarta Bay Marine Sediments

A laboratory study was conducted with the aim to isolate and identify bacteria from sea sediment and test their biodegradation ability in two place where contaminated with oil spill. Five sediment samples were dissolved by using sterile sea water, and then bacteria isolated with total plate count (TPC) method. Isolates bacteria was cultivated, and adapted using the nutrient conditioned sea water medium. Biodegradation process was done by mixing the bacteria with crude oil and shaken for few days. The number of bacteria isolated varied from 2 x 102 CFU ml-1 to 6 x 106 CFU ml-1 and apparently increased after cultivation and adaptation with oily media. Bacteria identified during this study were Fundibacter sp., Alcanivorax sp., and Marinobacter sp.. The result of biodegradation process was statistically analyzed and obtained that the bacteria are effective in degrading oil in seven days with constant of biodegradation rate was 0.1766. GC-MS analysis was conducted to prove the decomposition of carbon chain by bacteria and revealed oil degradation in carbon number 11 to 27. Based on all analysis, marine sediment bacteria can degrade the oil spill. Keywords : Bacteria, Biodegradation, GC-MS, Marine Sediments, Oil spill.

Contribution of airborne microbes to bacterial production and N2 fixation in seawater upon aerosol deposition

AbstractAerosol deposition may supply a high diversity of airborne microbes, which can affect surface microbial composition and biological production. This study reports a diverse microbial community associated with dust and other aerosol particles, which differed significantly according to their geographical air mass origin. Microcosm bioassay experiments, in which aerosols were added to sterile (0.2 µm filtered and autoclaved) SE Mediterranean Sea (SEMS) water, were performed to assess the potential impact of airborne bacteria on bacterial abundance, production, and N2 fixation. Significant increase was observed in all parameters within a few hours, and calculations suggest that airborne microbes can account for one third in bacterial abundance and 50–100% in bacterial production and N2‐fixation rates following dust/aerosol amendments in the surface SEMS. We show that dust/aerosol deposition can be a potential source of a wide array of microorganisms, which may impact microbial composition and food web dynamics in oligotrophic marine systems such as the SEMS.

Photochemical changes in water accommodated fractions of MC252 and surrogate oil created during solar exposure as determined by FT-ICR MS

To determine effects of photochemical weathering of petroleum, surrogate and Macondo (MC252) crude oils were exposed to solar radiation during the formation of Water Accommodated Fractions (WAFs) in sterile seawater. Samples were incubated in either unfiltered sunlight, with ultraviolet radiation blocked (Photosynthetically Active Radiation [PAR] only), or in darkness. WAFs were collected at two time points over the course of a week. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) analyses of water soluble species formed during exposure to sunlight were compared for the different treatments. Photochemical alterations resulted in differences in compound class distributions. In general, surrogate oil was photo-oxidized across a wider carbon number range compared to MC252. While photochemical differences were observed between MC252 and surrogate oils, microbial production in seawater responded similarly to both WAFs from both types of oils with the majority of the inhibition resulting from oil exposure to visible light.

Adverse Effects of ImmobilisedPseudoalteromonason the Fish PathogenicVibrio anguillarum:AnIn VitroStudy

As a prerequisite for use in marine aquaculture, two immobilisation systems were developed by employing the probiotic bacteriumPseudoalteromonassp. strain MLms_gA3. Their impact on the survivability of the fish pathogenVibrio anguillarumwas explored. Probiotic bacteria either grown as a biofilm on ceramic tiles or embedded in alginate beads were added to sterile artificial seawater that contained the fish pathogen. While immobilisation on ceramics followed a recently developed protocol, a medium allowing for alginate microencapsulation was newly developed. Anti-Vibrioactivities were obtained with both immobilisation systems. The viable cell counts ofV. anguillarumconstantly decreased within the first two weeks of the treatments evidencing the potential of the immobilisation systems for providing probiotic-based protection against this pathogen.

Settlement-Size Larval Red Drum (Sciaenops ocellatus) Respond to Estuarine Chemical Cues

Planktonic larvae combine directed swimming and functional sensory systems to locate benthic habitats. Some adult marine fishes use chemical cues for orientation to specific habitats, but olfactory function for estuarine fish larvae has received little research attention. This laboratory study quantified behavioral responses of red drum (Sciaenops ocellatus) larvae to estuarine chemical cues to examine the role of water chemistry as an orientation cue for locating or remaining in settlement habitat. Spontaneous activity (kinesis) was measured for pre-settlement-size larvae exposed to artificial sea water (as a negative control) and one of six treatments (sterilized sea water, sea water from a channel at ebb tide, sea water from a channel at flood tide, sea water from seagrass habitat, tannic acid dissolved in sterilized sea water, or lignin dissolved in sterilized sea water). Larvae that reached a size of competency to settle (approximately 10 mm standard length) swam faster when exposed to lignin dissolved in sterilized sea water than in other treatments; smaller larvae showed no response. Olfactory preference (taxis) was tested using a paired-choice experiment. Settlement-size larvae preferred water from seagrass beds to artificial sea water. The observed chemokinesis and chemotaxis in response to lignin dissolved in sterilized sea water and sea water from a seagrass bed demonstrate that red drum larvae can distinguish and respond to different water masses and suggest that chemical stimuli from seagrass settlement habitat may aid in orientation and movement to or retention in suitable settlement sites.

Adaptability of subtropical algae to local microbial populations

Marine algae found in the seagrass beds of the Florida Keys appear to be less susceptible to disease and die-offs reported for Thalassia testudinum. In the present study, we explore the hypothesis that algal antimicrobial chemical defenses are adapted to the microbial flora in their immediate microhabitat. To explore whether algal chemical defenses have co-evolved within their distinct microenvironments, we evaluated the inhibitory activities of algal extracts from twenty-four common algae in Florida seagrass beds against a panel of diverse marine bacteria. The panel of bacteria included strains isolated from the surface of the algae and from other aquatic and marine locales, including North Atlantic Ocean, Red Sea, and South Pacific Ocean, Iceland and the Great Lakes. Algal samples were placed in sterile seawater and sonicated for 5 minutes. Pieces of algae and seawater were plated separately on nutrient rich A1 or M1 plates. Sediment samples were diluted using sterile DI water, heat shocked at 37 ° C for 7 minutes, and added directly to nutrient-rich and -limited agar plates and allowed to incubate for 3 – 5 weeks. Individual colonies were isolated using nutrient rich freshwaterbased-A1 media. We analyzed the pattern of growth inhibition or promotion of algal extracts against co-isolated strains and those from other environments, and found that activity was not patterned on target strain phylogeny, but rather to isolation origin. Non-Floridian strains tended to either strong growth inhibition or promotion in response to many algal extracts, whereas co-isolated strains exhibited more nuanced patterns of activity, suggesting specific bacterial-algal interactions.

Influence of strain Bacillus cereus bacterium on corrosion behaviour of carbon steel in natural sea water

This paper examines the corrosion behaviours of carbon steel immersed in sterile natural sea water with and without strain Bacillus cereus. Electrochemical studies, including Tafel plots and electrochemical impedance spectroscopy (EIS) were performed to evaluate the variation of the corrosion behaviour of carbon steel in medium containing B. cereus as compared to the sterile control samples. The results of Tafel plot measurements showed significant reduction in the corrosion rate in the presence of bacterial biofilm produced by strain B. cereus. The EIS data showed that the charge transfer resistance is greater in a medium containing B. cereus and increases with immersion time.

THE CREATION OF NEWINTRANASALDRUGBASED ONRAW MATERIALSOF NATURAL ORIGINFORALLERGICRHINITISCOMBINED THERAPY

Allergic rhinitis is a disease of the nasal mucosa, which is based on allergic inflammation caused by the action of different natureallergens. Allergic rhinitis is quite common among the population, often occurs with frequent complications, resulting in decreased performance and quality of patients’life. Late or not effective therapy for this disease can lead to chronic disease and a combination of other pathologies, such as sinusitis, asthma and others.Primarily due to allergic inflammation in the lining of the nasal cavity,the allergen may persist for several weeks after exposure. Inflammation in the nasal cavitylining, triggered by allergens, leads to the accumulation of eosinophils, dendritic cells, T-lymphocytes and epithelial cells, which in its turn leads to activation and increased production of adhesion molecules by endothelial cells.Therapeutic help with allergic rhinitis may have the following areas:a) mechanical evacuation allergens;b) the use of pharmacological agents aimed at suppression of allergic process;c) the use of allergen-specific therapy;d) rational combination of the above directions for proper effect.Aim. Hold technological characteristics of salt dosage forms which are used as evacuation agents in the treatment of allergic rhinitis.Materials and methods. The material is known formulation, namely nasal saline solution. Information was taken from thesis, articles, patents and dissertation, etc.Results and discussion.Evacuation direction of curative care in allergic rhinitis caused by necessity of mechanical removal of allergens from the nasal cavity mucous areas. To do this, salt solutions of different compositionare used. According to the UkrainianState Register of medicines,salineis most common medicine in the domestic market amongpharmacotherapeutic group "means used for diseases of the nose". Range of nasal dosage forms is dominated by imported drugs, the share of domestic drugs is only 31.25%. As active ingredients, saline manufacturers mostly use sodium chloride, seawater and complex trace elements (magnesium, sodium, calcium) in different ratios. Such intranasal solutions by nature are mostly hypo or isotonic drugs. An exception is Aqua Maris® Strong (producer of "Jadran" Galenic Laboratory, Croatia), which is hypertonic solution of sterile seawater. As the solvent purified water or water for injectionare used. To ensure the stability of nasal dosage forms, some manufacturers of the tracks added preservatives, derivatives of quaternary ammonium compounds (benzalkonium chloride) and aromatic alcohols (benzyl alcohol). To normalize the pH substances of different chemical nature, such as sodium hydrogen phosphate dihydrate, sodium dihydrogen phosphate dihydrate, hydrochloric acidare used.Despite the existing range of drugs aimed at treatment and prevention of allergic rhinitis in patients,there is currentlyno safe and effectivetool that can fully provide therapeutic effect. When developing new means for intranasal pharmacotherapy of allergic rhinitis it is rational touse minerals of national origin, which will not only provide evacuation allergens, but also due to its high quality components will implement anti-inflammatory activity.Conclusions. As a result of research it was conducted that among intranasal medicines the natural salt is used for the treatment and prevention of allergic rhinitis. It is established that complex magnesium minerals from raw materials of natural originare perspective to be used.

Bacteria‐driven production of alkyl nitrates in seawater

AbstractAircraft‐ and ship‐borne measurements have shown that the ocean is a large, diffuse source for short chain (C1–C3) gas phase alkyl nitrates (RONO2). Photochemical production of RONO2 has been demonstrated previously as a viable mechanism in surface waters; however, it cannot account for the observed depth profile of RONO2, suggesting an additional, dark RONO2 production mechanism. We present measurements of gas phase C1–C5 alkyl nitrates emitted from seawater in a controlled mesocosm experiment conducted under low‐light conditions in a glass‐walled wave channel. Ethyl and butyl nitrate emission rates from seawater are strongly correlated with the abundance of heterotrophic bacteria (R2 ≥ 0.89) and show no correlation to chlorophyll a concentration. Controlled flask experiments conducted using ambient and sterile seawater, inoculated with a heterotrophic bacterium, confirm that bacterial driven production of select RONO2 can proceed efficiently in the absence of light.

Cryopreservation of filaments of Scytosiphon lomentaria by vitrification

Filaments of the brown alga, Scytosiphon lomentaria cultured in our laboratory were cryopreserved at −20 °C using a vitrification procedure. We investigated the effects of different loading solutions (LS), vitrification solutions (VS), loading times, and dehydration times on the viability of cryopreserved filaments of S. lomentaria. The highest survival rate (38.42 %) was achieved when filaments of S. lomentaria were loaded with LS5 for 30 min, dehydrated with VS2 for 30 min at 0 °C, cryopreserved instantly and then kept at −20 °C for 1 month, then rewarmed at 40 °C in a water bath, rinsed with 1.2 M sucrose for 20 min, and cultured in sterile seawater for 2 days. The filaments recovered after cryopreservation showed the same morphology and growth as non-cryopreserved filaments. The recovered filaments were able to produce normal sporangia, which released viable spores. Compared with non-cryopreserved filaments, the cryopreserved filaments produced fewer sporangial branchlets and fewer spores. However, the spores released by cryopreserved filaments of S. lomentaria showed strong vitality and were able to grow into normal, healthy thalli.

Effect of Salinity on the Effectiveness of Solidifiers for Crude Oil Spill Remediation

ABSTRACT A laboratory investigation was conducted to test the effectiveness of solidifiers with fresh water and artificial seawater using Prudhoe Bay Crude oil. Experiments were designed to study the effects of salinity, solidifier type, solidifier-to-oil mass ratio (SOR), mixing energy and beaker size using five solidifiers. The U.S. Environmental Protection Agency is developing a protocol for testing the effectiveness of solidifiers in a laboratory setting. This involves measuring the amount of free oil remaining in the water after the solidified product is removed using an ultraviolet–visible spectrophotometer. For these experiments, 0.25 mL of oil was added to salinized beaker containing 80 mL of water. Milli-Q water and sterile GP2 seawater were used as the exposure media. The mass of the solidifier was changed depending on the SOR. Each of the solidifier was added to a slick of crude oil on water. After stirring the mixture for 30 minutes, the solidifier was removed. The water with the remaining oil was transferred from the beaker to 250 mL separatory funnel. The solution in the funnel was extracted three times with 20 mL of dichloromethane and the final volume adjusted to 60 mL. The extracted samples were analyzed for oil content with an Agilent 8452 ultraviolet–visible spectrophotometer. All experiments were carried out in triplicate. An analysis of variance (ANOVA) was performed on the data collected, which helped quantify the main and interactive effects of the variables. Salinity of the water was mostly found to be an insignificant factor. Results indicated that SOR and solidifier type are the most important variables affecting removal efficiency.

Infectious Salmon Anemia (ISA) Virus: Infectivity in Seawater under Different Physical Conditions

Infectious salmon anemia (ISA) virus (genus Isavirus, family Orthomyxoviridae), present in all major salmon producing countries, is the causative agent for a serious and commercially important disease affecting Atlantic Salmon Salmo salar. Nearly all ISA outbreaks occur in the marine production phase and knowledge about survival time for ISA virions in seawater is crucial for an adequate strategy to combat the disease. To acquire knowledge about this important factor, a study of ISA virus exposed to four different physical conditions was carried out. The virions' survival was tested in sterile seawater, sterile seawater with normal ultraviolet light radiation (UVR), natural seawater, and natural seawater with UVR. During the 72-h experiment both presence of ISA virus RNA and the infectivity of ISA virions were monitored. The result of this study showed that the infectivity of ISA virions is lost within 3 h of exposure to natural seawater or sterile seawater with UVR. However, it was possible to detect ISA virus RNA throughout the experimental period. This indicates that the effect of both UVR and biological activity of natural seawater limits the survival time of ISA virions under normal conditions. The survival time of ISA virions in sterile seawater was less than 24 h. Based on the available literature and the present study it is not very likely that passive horizontal transmission in seawater over long distances can occur. This is due to the following factors: (1) the effect of UVR and biological activity on ISA virions infectivity found in the present study, (2) the speed and dilution effect in seawater currents in salmon farming areas, (3) the temperature during the major outbreak periods, and (4) the need for an infective dose of ISA virions to reach naive Atlantic Salmon.

Uptake and Localization of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus in Blue Mussels (Mytilus edulis) of the Baltic Sea

ABSTRACT Species of Vibrio can persist in blue mussels, especially when they are present in high numbers as a result of a large uptake from the aquatic environment. This study investigated the uptake, localization, and persistence of three Vibrio species relevant to human health in blue mussels (Mytilus edulis) after artificial contamination. Mussels M. edulis were kept in tanks of artificial seawater spiked with Vibrio spp. to monitor bioaccumulation of these bacteria in corresponding bivalves. Bacteria accumulated rapidly in the bivalves, reaching high concentrations after 1.5 h. The highest Vibrio sp. counts were detected in the digestive glands, with 6.9 × 108 cfu/g for Vibrio parahaemolyticus, 1.5 × 107 cfu/g for Vibrio cholerae, and 2.2 × 107 cfu/g for Vibrio vulnificus. Among bivalve compartments, the digestive glands showed the fastest enrichment of Vibrio and maintained the highest Vibrio numbers throughout the examination period. After transfer to a tank containing filtered, sterile seawater, th...

Pseudoalteromonas spp. Serve as Initial Bacterial Attractants in Mesocosms of Coastal Waters but Have Subsequent Antifouling Capacity in Mesocosms and when Embedded in Paint

The purpose of the present study was to determine if the monoculture antifouling effect of several pigmented pseudoalteromonads was retained in in vitro mesocosm systems using natural coastal seawater and when the bacteria were embedded in paint used on surfaces submerged in coastal waters. Pseudoalteromonas piscicida survived on a steel surface and retained antifouling activity for at least 53 days in sterile seawater, whereas P. tunicata survived and had antifouling activity for only 1 week. However, during the first week, all Pseudoalteromonas strains facilitated rather than prevented bacterial attachment when used to coat stainless steel surfaces and submerged in mesocosms with natural seawater. The bacterial density on surfaces coated with sterile growth medium was 10(5) cells/cm(2) after 7 days, whereas counts on surfaces precoated with Pseudoalteromonas were significantly higher, at 10(6) to 10(8) cells/cm(2). However, after 53 days, seven of eight Pseudoalteromonas strains had reduced total bacterial adhesion compared to the control. P. piscicida, P. antarctica, and P. ulvae remained on the surface, at levels similar to those in the initial coating, whereas P. tunicata could not be detected. Larger fouling organisms were observed on all plates precoated with Pseudoalteromonas; however, plates coated only with sterile growth medium were dominated by a bacterial biofilm. Suspensions of a P. piscicida strain and a P. tunicata strain were incorporated into ship paints (Hempasil x3 87500 and Hempasil 77500) used on plates that were placed at the Hempel A/S test site in Jyllinge Harbor. For the first 4 months, no differences were observed between control plates and treated plates, but after 5 to 6 months, the control plates were more fouled than the plates with pseudoalteromonad-based paint. Our study demonstrates that no single laboratory assay can predict antifouling effects and that a combination of laboratory and real-life methods must be used to determine the potential antifouling capability of new agents or organisms.

Poly I:C induces a protective antiviral immune response in the Pacific oyster (Crassostrea gigas) against subsequent challenge with Ostreid herpesvirus (OsHV-1 μvar)

In-vivo studies were carried out to investigate the protective effect of a synthetic viral analogue (poly I:C) against Ostreid herpes virus (OsHV-1 μvar). Pacific oysters (Crassostrea gigas) were immune-primed by intramuscular injection of 240 μg of poly I:C or sterile seawater at 1 day prior to infection with OsHV-1 μvar. Poly I:C injection induced an antiviral state in C. gigas as the percentage of viral-infected oysters at 48 h post infection was significantly lower in the poly I:C treatment (11%) compared to seawater controls (100%). In an additional experiment, we demonstrated that the protective role of poly I:C is reproducible and elicits a specific antiviral response as immune-priming with heat-killed Vibrio splendidus provided no protection against subsequent viral infection. In both experiments, genes homologous to a toll-like receptor (TLR), MyD88, interferon regulatory factor (IRF) and protein kinase R (PKR) were up-regulated in oysters immune-primed with poly I:C compared to seawater controls (p < 0.05). The MyD88, IRF and PKR genes were also significantly up-regulated in response to OsHV-1 μvar infection (p < 0.05), which is suggestive that they are implicated in the antiviral response of C. gigas. Our results demonstrate that C. gigas can recognise double-strand RNA to initiate an innate immune response that inhibits viral infection. The observed response has striking similarities to the hallmarks of the type-1 interferon response of vertebrates.

Phaeobactergrown in biofilters: a new strategy for the control ofVibrionaceaein aquaculture

Growth, biofilm formation, antagonism and residence time in green seawater tanks maintained under fish rearing conditions of Phaeobacter 27-4 were studied in commercial biofilters made from plastic, sintered glass and ceramic. Phaeobacter reached 108–109 CFU cm−3 and formed rosettes in all materials, but a multilayer biofilm was only observed in the ceramic biofilters. In sterile seawater, plastic and ceramic biofilters reduced Vibrio anguillarum and V. splendidus concentration in one-two Log after 24–48 h, showing 102–103 CFU mL−1. Sintered glass biofilters only inactivated V. anguillarum. In Marine Broth, sintered glass and ceramic biofilters inhibited V. anguillarum growth in two-three Log, showing 104–105 CFU mL−1 after 24 h. Plastic biofilters reduced V. anguillarum concentration in one Log after 48 h. V. splendidus growth was only inhibited by sintered glass and ceramic biofilters in one-two Log, showing 107 CFU mL−1 after 24 h. Phaeobacter also diminished biofilters colonization by the pathogens, both in seawater and in MB. Phaeobacter residence time in green seawater tanks maintained under fish rearing conditions was longer with sintered glass and ceramic biofilters. The latest showed the lowest detachment and, after 11 days, Phaeobacter (106 bacteria·cm−3) covered more than 80% of biofilters total culturable bacteria. DGGE profiles showed that Phaeobacter biofilters stabilizes the green seawater bacterial microbiota.

Specificity of Associations between Bacteria and the Coral Pocillopora meandrina during Early Development

Relationships between corals and specific bacterial associates are thought to play an important role in coral health. In this study, the specificity of bacteria associating with the coral Pocillopora meandrina was investigated by exposing coral embryos to various strains of cultured marine bacteria, sterile seawater, or raw seawater and examining the identity, density, and location of incorporated cells. The isolates utilized in this experiment included members of the Roseobacter and SAR11 clades of the Alphaproteobacteria, a Pseudoalteromonas species of the Gammaproteobacteria, and a Synechococcus species of the Cyanobacteria phylum. Based on terminal restriction fragment length polymorphism analysis of small-subunit rRNA genes, similarities in bacterial communities associated with 170-h-old planulae were observed regardless of treatment, suggesting that bacteria may have been externally associated from the outset of the experiment. Microscopic examination of P. meandrina planulae by fluorescence in situ hybridization with bacterial and Roseobacter clade-specific oligonucleotide probes revealed differences in the densities and locations of planulae-associated cells. Planulae exposed to either raw seawater or strains of Pseudoalteromonas and Roseobacter harbored the highest densities of internally associated cells, of which 20 to 100% belonged to the Roseobacter clade. Planulae exposed to sterile seawater or strains of the SAR11 clade and Synechococcus did not show evidence of prominent bacterial associations. Additional analysis of the raw-seawater-exposed planulae via electron microscopy confirmed the presence of internally associated prokaryotic cells, as well as virus-like particles. These results suggest that the availability of specific microorganisms may be an important factor in the establishment of coral-bacterial relationships.

Biocorrosion of stainless steel 316 in seawater: inhibition using an azole type derivative

Corrosion inhibition of stainless steel 316 (SS316) by 2-methylbenzimidazole (MBI) in sterile enriched artificial seawater and seawater with sulphate reducing bacteria (SRB) was investigated using direct current polarisation, electrochemical impedance spectroscopy, confocal laser scanning microscopy and atomic force microscopy. It is shown that MBI is an effective inhibitor in controlling the abiotic corrosion of SS316 and as well as biocorrosion by two strains of SRB (i.e. Desulfovibrio desulfuricans and Desulfovibrio singaporenus). The MBI effectively inhibits biocorrosion of SS316 by both D. desulfuricans and D. singaporenus, with >90% inhibition efficiency.

Influence of Pseudomonas on corrosion and mechanical properties of carbon steel in sea water

In order to separate the effects of a specific microbial species (Pseudomonas) in sea water on carbon steel, a comparative study of the corrosion and mechanical properties of AISI 1045 carbon steel in natural sea water, sterile sea water and Pseudomonas inoculated sea water was carried out using tensile testing, mass loss experiments and microscopy. The results of mass loss showed that the corrosion rate of the specimens in the single Pseudomonas system was faster than that in sterile sea water but slower than in natural sea water. Microscopy revealed that a loose corrosion product layer formed on the surface of carbon steel, and micropitting corrosion occurred underneath the corrosion product. Energy dispersive X-ray analysis of this deposit indicated that iron and oxygen were the main components, and a large amount of carbon, which most likely originated from the bacteria and its exopolymer, could also be detected. The tensile strength of carbon steel was reduced by the action of Pseudomonas, but hydrogen embrittlement was not found.