Bacteria flora and heavy metals in cultivated oysters Crassostrea iredalei of Setiu Wetland, East Coast Peninsular Malaysia

Abstract

Slipper oyster Crassostrea iredalei is a species of good demand for its sweet flavor and white coloured flesh. The filter feeding nature predisposes oysters to accumulation of pathogenic and heavy metals in waters impacted by sewage pollutions and may thus render the oysters unfit for human consumption. A study was undertaken to investigate the presence of bacteria flora and heavy metal concentrations in cultivated oysters Crassostrea iredalei at Setiu Wetland, Terengganu, the only source of cultivated oysters in East Coast of Malaysia. A total of 200 slipper oyster samples were analyzed. The bacteria were isolated using non selective agar such as TSA agar and selective agars before they were then identified using conventional methods in combination with BBL Crystal identification kit. Heavy metals such as zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb) concentrations were determined using atomic absorption spectrophotometry. Results showed that the oysters harbor predominantly Shewanella putrifaciens followed by Vibrio parahaemolyticus, Vibrio vulnificus, Vibrio cholerae, Enterobacter cloacae, Escherichia coli and Chromobacterium violaceum. They also contain high concentration of Zn (785.68 +/- 285.88 microg/g) with the lowest heavy metal was Pb (0.17 +/- 0.15 microg/g), whilst the concentrations of other heavy metals were Cu (38.9 +/- 13.2 microg/g) and Cd (1.60 +/- 0.28 microg/g). The study is very useful to evaluate the type of bacteria and heavy metal present in oyster meat for human consumption.

Molecular Analysis of Bacterial Microbiota Associated with Oysters (Crassostrea gigas and Crassostrea corteziensis) in Different Growth Phases at Two Cultivation Sites

“…The α-, β-, and γ-Proteobacteria, Firmicutes, Spirochaetes, and Actinobacteria species that we identified among the microbiota associated with C. gigas or C. corteziensis have been reported in other oysters using cultureindependent techniques [33,40,54,63,69]. However, our results showed low bacterial diversity compared with other studies.…”

“…The Vibrio and Pseudomonas species are commonly isolated from oyster tissues using traditional methods [31,54,62,63,75,77] and are recognized as symbionts of diverse marine invertebrates [32]. In general, the Vibrios species have been reported in sick oysters and have been detected using selective culturing [17,59,75,76].…”

“…In some cases, studies have demonstrated diseases of bacterial etiology, including vibrioses nocardosis and infections by Chlamydia-, Mycoplasma-, and Rickettsia-like organisms [7,39,59,65,68,75]. Because oysters may concentrate pathogenic microorganisms, the microbiota of oysters have been examined mainly from the public health perspective, and most of the studies have focused on fecal contamination, enteric pathogens, and pathogenic species of Vibrio [17,34,39,54,67,[75][76][77].…”

“…In recent years, the natural bacterial microbiota of different oysters (Crassostrea gigas [33], Crassostrea virginica [40], Saccostrea glomerata [29], Ostrea chilensis [69], and Crassostrea iredalei [54]) have been described. However, these studies do not focus on the changes in microbiota that may occur during the growth of the oysters.…”

Changes in the composition and diversity of the bacterial microbiota associated with oysters (Crassostrea corteziensis,Crassostrea gigasandCrassostrea sikamea) during commercial production

“…), which are bacteria that are commonly found in the marine environment. The great bacterial diversity that was observed in this study has not been reported for these or other oyster species (Pujalte et al ., ; Najiah et al ., ; Green & Barnes, ; Zurel et al ., ; Fernández‐Piquer et al ., ), and most are recently discovered. The adult and postlarvae stages showed different Proteobacteria community structures.…”