Phylogenetic analysis of intestinal bacteria in the Chinese mitten crab (Eriocheir sinensis)

AIMS: To identify the dominant intestinal bacteria in the Chinese mitten crab, and to investigate the differences in the intestinal bacteria between pond-raised and wild crabs. METHODS AND RESULTS: The diversity of intestinal bacteria in the Chinese mitten crabs was investigated by denaturing gradient gel electrophoresis (DGGE) fingerprinting, 16S rRNA gene clone library analysis and real-time quantitative PCR. The principal component analysis of DGGE profiles indicated that substantial intersubject variations existed in intestinal bacteria in pond-raised crab. The sequencing of 16S rRNA genes revealed that 90-95% of the phylotypes in the clone libraries were affiliated with Proteobacteria and Bacteroidetes. Some genera were identified as unique in wild crabs and in pond-raised crabs, whereas Bacteroidetes was found to be common in all sampled crab groups. Real-time quantitative PCR indicated that the abundance of Bacteroides and the total bacterial load were approximately four-to-10 times higher in pond-raised crabs than in wild crabs. A significant portion of the phylotypes shared low similarity with previously sequenced organisms, indicating that the bacteria in the gut of Chinese mitten crabs are yet to be described. CONCLUSIONS: The intestinal bacteria of pond-raised crabs showed higher intersubject variation, total diversity and abundance than that observed in wild crabs. The high proportion of the clones of Proteobacteria and Bacteroidetes in the clone library is an indication that these bacteria may be the dominant population in the gut of the Chinese mitten crab. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated obvious differences in the intestinal bacterial composition of pond-raised crabs and wild crabs. This knowledge will increase our understanding of the effects of aquaculture operations on bacterial community composition in the crab gut and provide necessary data for the development of probiotic products for crab cultivation.     

An integrated overview of the bacterial flora composition of Hyalomma anatolicum,the main vector of CCHF

The microbial flora associated with Hyalomma anatolicum ticks was investigated using culture-dependent (CD) and independent (next generation sequencing, NGS) methods. The bacterial profiles of different organs, development stages, sexes, and of host cattle skins were analyzed using the CD method. The egg and female gut microbiota were investigated using NGS. Fourteen distinct bacterial strains were identified using the CD method, of which Bacillus subtilis predominated in eggs, larval guts and in adult female and male guts, suggesting probable transovarial transmission. Bacillus velezensis and B. subtilis were identified in cattle skin and tick samples, suggesting that skin is the origin of tick bacteria. H.anatolicum males harbour lower bacterial diversity and composition than females. The NGS analysis revealed five different bacterial phyla across all samples, Proteobacteria contributing to >95% of the bacteria. In all, 56611sequences were generated representing 6,023 OTUs per female gut and 421 OTUs per egg. Francisellaceae family and Francisella make up the vast majority of the OTUs. Our findings are consistent with interference between Francisella and Rickettsia. The CD method identified bacteria, such B. subtilis that are candidates for vector control intervention approaches such paratransgenesis whereas NGS revealed high Francisella spp. prevalence, indicating that integrated methods are more accurate to characterize microbial community and diversity.     

Invasion biology of the Chinese mitten crab Eriochier sinensis: A brief review

The Chinese mitten crab Eriocheir sinensis is a native of freshwater and estuarine habitats along the east coast of Asia. Invasive populations have existed in northern Europe since the early 20th century, and more recently a breeding population has become established in the San Francisco Bay system along the west coast of North America. Ballast water is the most probable vector for both invasions, although there is also potential for escape from ethnic markets and from the ornamental aquarium industry. Invasive populations of mitten crabs have caused millions of dollars in economic and ecological damage. Economic impacts center largely on the burrowing activity of the crabs, which damages stream banks and levees, and the annual spawning migration, which interferes with fishing activities and irrigation projects. Chinese mitten crabs have recently appeared in the Chesapeake and Delaware Bays on the east coast of the USA, and there are confirmed reports of breeding females in both estuaries. The potential for large populations of mitten crabs in these estuaries has not been determined. This paper presents a review of the biology and ecology of native and invasive populations of the species and provides recommendations for research relevant to the prediction of future mitten crab invasions.     

The inconstant gut microbiota of Drosophila species revealed by 16S rRNA gene analysis

The gut microorganisms in some animals are reported to include a core microbiota of consistently associated bacteria that is ecologically distinctive and may have coevolved with the host. The core microbiota is promoted by positive interactions among bacteria, favoring shared persistence; its retention over evolutionary timescales is evident as congruence between host phylogeny and bacterial community composition. This study applied multiple analyses to investigate variation in the composition of gut microbiota in drosophilid flies. First, the prevalence of five previously described gut bacteria (Acetobacter and Lactobacillus species) in individual flies of 21 strains (10 Drosophila species) were determined. Most bacteria were not present in all individuals of most strains, and bacterial species pairs co-occurred in individual flies less frequently than predicted by chance, contrary to expectations of a core microbiota. A complementary pyrosequencing analysis of 16S rRNA gene amplicons from the gut microbiota of 11 Drosophila species identified 209 bacterial operational taxonomic units (OTUs), with near-saturating sampling of sequences, but none of the OTUs was common to all host species. Furthermore, in both of two independent sets of Drosophila species, the gut bacterial community composition was not congruent with host phylogeny. The final analysis identified no common OTUs across three wild and four laboratory samples of D. melanogaster. Our results yielded no consistent evidence for a core microbiota in Drosophila. We conclude that the taxonomic composition of gut microbiota varies widely within and among Drosophila populations and species. This is reminiscent of the patterns of bacterial composition in guts of some other animals, including humans.     

Crayfish co-introduced symbiotic ostracod found on native crab in Japan: The first record of epibiont ostracod found a new host

Ankylocythere sinuosa (Rioja, 1942), a symbiotic ostracod native to North America, was found from the Japanese mitten crab Eriocheir japonica (De Haan, 1835), a species native to Japan, collected from a pond in Shizuoka City, Shizuoka Prefecture, central Japan. Introduced North American crayfish Procambarus clarkii (Girard, 1852), which is a host of A. sinuosa in their native range, inhabits ponds sympatrically with Japanese mitten crabs, and it is thought that the ostracods transferred from the exotic crayfish to the native crabs. In recent years, along with the artificial transportation of crayfish around the world, their symbiotic ostracods also have been found on the body surfaces of exotic crayfish in Europe and Japan. However, no studies have confirmed the infestation of exotic ostracods on native crustaceans in the field. A wide range of developmental stages of A. sinuosa from juveniles to adults were found in Japanese mitten crabs, and mating individuals were also found. This strongly suggests that they can reproduce on the body surface of Japanese mitten crabs. In the future, it will be necessary to strengthen measures against alien species to prevent these exotic symbionts from infestating native ecosystems, and we also need to investigate the exact impact of this symbiont on Japanese mitten crabs.     

Gill Phospholipids of Mitochondria in Euryhaline Crustaceans as Related to Changes in Environmental Salinity

The distribution of different phospholipids and their variation in fatty acids composition were studied in mitochondrial fractions isolated from anterior and posterior gills of the two euryhaline crabs, Enocheir sinensis and Carcinus maenas, as a function of the environmental salinity. No matter what the salinity, the three more posterior located gills of E. sinensis were shown to contain more unsaturated phospholipids (PE, DPG) and more eicosapentaanoic acids (20:5ω 3) than the three more anterior ones. This was particularly significant when crabs were acclimatized to fresh water. The lipid content of the anterior and posterior gills of the seashore crab C. maenas, on the contrary, showed no significant differences. These results are discussed by taking into consideration the different osmo- and ion-regulation capabilities of the two euryhaline crabs studied and it is proposed that a possible viscotropic regulation might check the activity of membrane-bound enzymes among which the (Na⁺ + K⁺)-ATPase related to the Na⁺-active transport processes involved in maintaining Na⁺ balance.     

Pyrosequencing analysis of the bacterial communities in the guts of honey bees Apis cerana and Apis mellifera in Korea

The bacterial communities in the guts of the adults and larvae of the Asian honey bee Apis cerana and the European honey bee Apis mellifera were surveyed by pyrosequencing the 16S rRNA genes. Most of the gut bacterial 16S rRNA gene sequences were highly similar to the known honey bee-specific ones and affiliated with Pasteurellaceae or lactic acid bacteria (LAB). The numbers of operational taxonomic units (OTUs, defined at 97% similarity) were lower in the larval guts (6 or 9) than in the adult guts (18 or 20), and the frequencies of Pasteurellaceae-related OTUs were higher in the larval guts while those of LAB-related OTUs in the adult guts. The frequencies of Lactococcus, Bartonella, Spiroplasma, Enterobacteriaceae, and Flavobacteriaceae-related OTUs were much higher in A. cerana guts while Bifidobacterium and Lachnospiraceae-related OTUs were more abundant in A. mellfera guts. The bacterial community structures in the midguts and hindguts of the adult honey bees were not different for A. cerana, but significantly different for A. mellifera. The above results substantiated the previous observation that honey bee guts are dominated by several specific bacterial groups, and also showed that the relative abundances of OTUs could be markedly changed depending on the developmental stage, the location within the gut, and the honey bee species. The possibility of using the gut bacterial community as an indicator of honey bee health was discussed.     

Molecular Cloning and Gene Expression Analysis of the Leptin Receptor in the Chinese Mitten Crab Eriocheir sinensis

Background

Leptin is an adipocyte-derived hormone with multiple functions that regulates energy homeostasis and reproductive functions. Increased knowledge of leptin receptor function will enhance our understanding of the physiological roles of leptin in animals.

Methodology/Principal Findings

In the present study, a full-length leptin receptor (lepr) cDNA, consisting of 1,353 nucleotides, was cloned from Chinese mitten crab (Eriocheir sinensis) using rapid amplification of cDNA ends (RACE) following the identification of a single expressed sequence tag (EST) clone in a cDNA library. The lepr cDNA consisted of a 22-nucleotide 5′-untranslated region (5′ UTR), a 402-nucleotide open reading frame (ORF) and a 929-nucleotide 3′ UTR. Multiple sequence alignments revealed that Chinese mitten crab lepr shared a conserved vacuolar protein sorting 55 (Vps55) domain with other species. Chinese mitten crab lepr expression was determined in various tissues and at three different reproductive stages using quantitative real-time RT-PCR. Lepr expression was highest in the intestine, thoracic ganglia, gonad, and accessory gonad, moderate in hepatopancreas and cranial ganglia, and low in muscle, gill, heart, haemocytes, and stomach. Furthermore, lepr expression was significantly higher in the intestine, gonad and thoracic ganglia in immature crabs relative to precocious and mature crabs. In contrast, lepr expression was significantly lower in the hepatopancreas of immature crabs relative to mature crabs.

Conclusions/Significance

We are the first to identify the lepr gene and to determine its gene expression patterns in various tissues and at three different reproductive stages in Chinese mitten crab. Taken together, our results suggest that lepr may be involved in the nutritional regulation of metabolism and reproduction in Chinese mitten crabs.     

Effects of the complete replacement of fish oil with linseed oil on growth,fatty acid composition,and protein expression in the Chinese mitten crab (<Emphasis Type="Italic">Eriocheir sinensis</Emphasis>)

Background

The finite marine resources make it difficult for us to obtain enough fish oil (FO) used in aquatic feeds. Another sustainable ingredients should be found to substitute FO. The effects of replacing FO with vegetable oil have been studied in a variety of crustaceans, but most studies have focused on the phenotypic effects. Little is known about the mechanisms of the effects.

Methods

To understand the molecular responses during the replacement of FO in Eriocheir sinensis, we investigated the effects of feeding FO or linseed oil (LO) on growth performance, digestive enzyme activity, fatty acid composition and protein expression in E. sinensis. Twenty-four juvenile crabs were fed diets containing FO or LO for 112 days. Weight, carapace length and width were recorded. Fatty acid composition of the diets and the hepatopancreas and protein expression in the hepatopancreas were analyzed.

Results

Growth performance and molting interval were unchanged by diet. Crabs fed FO and LO had same activity of lipase and amylase, but comparing with crabs fed LO, crabs fed FO had higher trypsin activity and lower pepsin activity. Hepatopancreas fatty acid composition changed to reflect the fatty acid composition of the diets. In total, 194 proteins were differentially expressed in the hepatopancreas between the diets. Expression of heat shock proteins was higher in crabs fed LO. Expression of fatty acid synthase, long-chain fatty acid transport protein 4, acyl-CoA delta-9 desaturase, and fatty acid-binding protein 1, was higher in crabs fed FO.

Conclusions

The substitution of FO with LO didn’t have any effects on the growth and molting of mitten crab, but could significantly decrease the ability of mitten crab to cope with stress. The high content of HUFAs in the hepatopancreas of mitten crab fed FO is due to the high abundance of the proteins relative to the transport of the HUFAs. These findings provide a reason of the high content of EPA and DHA in crabs fed with FO, and provide new information for the replacement of FO in diets of mitten crab.

     

Diversity of the intestinal microbiota in different patterns of feeding infants by Illumina high-throughput sequencing

The gastrointestinal microbiota plays a crucial role in the health and disease of the host through its impact on nutrition. Gut microbial composition is related to different diets, but an association of microbiota with different diets in infant has not yet been shown. In this work, we compared the fecal microbiota of breast-fed (BF) and formula-fed infants (FF). By using Illumina high-throughput sequencing and biochemical analyses, we found differences in gut microbiota between the two groups. BF infants showed a significant enrichment of Actinobacteria and Firmicutes and depletion of Proteobacteria (P < 0.05), the abundance of Bacteroidetes in the two groups was very low (P > 0.05). Enterobacteriaceae (Proteobacteria) were the dominant bacteria in FF infant fecal microbiota, and Veillonellaceae (Firmicutes) and Enterobacteriaceae (Proteobacteria) were the dominant bacteria in the BF infant fecal microbiota. The number of genera (percentage of sequences >0.1 %) in BF and FF infants was 17 and 15 respectively, and Streptococcus was the dominant bacterial genus in both groups.     

Stability of Sponge-Associated Bacteria over Large Seasonal Shifts in Temperature and Irradiance

Complex microbiomes reside in marine sponges and consist of diverse microbial taxa, including functional guilds that may contribute to host metabolism and coastal marine nutrient cycles. Our understanding of these symbiotic systems is based primarily on static accounts of sponge microbiota, while their temporal dynamics across seasonal cycles remain largely unknown. Here, we investigated temporal variation in bacterial symbionts of three sympatric sponges (Ircinia spp.) over 1.5 years in the northwestern (NW) Mediterranean Sea, using replicated terminal restriction fragment length polymorphism (T-RFLP) and clone library analyses of bacterial 16S rRNA gene sequences. Bacterial symbionts in Ircinia spp. exhibited host species-specific structure and remarkable stability throughout the monitoring period, despite large fluctuations in temperature and irradiance. In contrast, seawater bacteria exhibited clear seasonal shifts in community structure, indicating that different ecological constraints act on free-living and on symbiotic marine bacteria. Symbiont profiles were dominated by persistent, sponge-specific bacterial taxa, notably affiliated with phylogenetic lineages capable of photosynthesis, nitrite oxidation, and sulfate reduction. Variability in the sponge microbiota was restricted to rare symbionts and occurred most prominently in warmer seasons, coincident with elevated thermal regimes. Seasonal stability of the sponge microbiota supports the hypothesis of host-specific, stable associations between bacteria and sponges. Further, the core symbiont profiles revealed in this study provide an empirical baseline for diagnosing abnormal shifts in symbiont communities. Considering that these sponges have suffered recent, episodic mass mortalities related to thermal stresses, this study contributes to the development of model sponge-microbe symbioses for assessing the link between symbiont fluctuations and host health.     

Insect Gut Bacterial Diversity Determined by Environmental Habitat,Diet, Developmental Stage,and Phylogeny of Host

Insects are the most abundant animals on Earth, and the microbiota within their guts play important roles by engaging in beneficial and pathological interactions with these hosts. In this study, we comprehensively characterized insect-associated gut bacteria of 305 individuals belonging to 218 species in 21 taxonomic orders, using 454 pyrosequencing of 16S rRNA genes. In total, 174,374 sequence reads were obtained, identifying 9,301 bacterial operational taxonomic units (OTUs) at the 3% distance level from all samples, with an average of 84.3 (±97.7) OTUs per sample. The insect gut microbiota were dominated by Proteobacteria (62.1% of the total reads, including 14.1% Wolbachia sequences) and Firmicutes (20.7%). Significant differences were found in the relative abundances of anaerobes in insects and were classified according to the criteria of host environmental habitat, diet, developmental stage, and phylogeny. Gut bacterial diversity was significantly higher in omnivorous insects than in stenophagous (carnivorous and herbivorous) insects. This insect-order-spanning investigation of the gut microbiota provides insights into the relationships between insects and their gut bacterial communities.     

Bacterial Community Associated with Organs of Shallow Hydrothermal Vent Crab Xenograpsus testudinatus near Kuishan Island,Taiwan

Shallow-water hydrothermal vents off Kueishan Island (northeastern Taiwan) provide a unique, sulfur-rich, highly acidic (pH 1.75–4.6) and variable-temperature environment. In this species-poor habitat, the crab Xenograpsus testudinatus is dominant, as it mainly feeds on zooplankton killed by sulfurous plumes. In this study, 16S ribosomal RNA gene amplicon pyrosequencing was used to investigate diversity and composition of bacteria residing in digestive gland, gill, stomach, heart, and mid-gut of X. testudinatus, as well as in surrounding seawater. Dominant bacteria were Gamma- and Epsilonproteobacteria that might be capable of autotrophic growth by oxidizing reduced sulfur compounds and are usually resident in deep-sea hydrothermal systems. Dominant bacterial OTUs in X. testudinatus had both host and potential organ specificities, consistent with a potential trophic symbiotic relationship (nutrient transfer between host and bacteria). We inferred that versatile ways to obtain nutrients may provide an adaptive advantage for X. testudinatus in this demanding environment. To our knowledge, this is the first study of bacterial communities in various organs/tissues of a crustacean in a shallow-water hydrothermal system, and as such, may be a convenient animal model for studying these systems.     

Fatty Acid Binding Proteins FABP9 and FABP10 Participate in Antibacterial Responses in Chinese Mitten Crab,Eriocheir sinensis

Invertebrates rely solely on the innate immune system for defense against pathogens and other stimuli. Fatty acid binding proteins (FABP), members of the lipid binding proteins superfamily, play a crucial role in fatty acid transport and lipid metabolism and are also involved in gene expression induced by fatty acids. In the vertebrate immune system, FABP is involved in inflammation regulated by fatty acids through its interaction with peroxidase proliferator activate receptors (PPARs). However, the immune functions of FABP in invertebrates are not well characterized. For this reason, we investigated the immune functionality of two fatty acid binding proteins, Es-FABP9 and Es-FABP10, following lipopolysaccharide (LPS) challenge in the Chinese mitten crab (Eriocheir sinensis). An obvious variation in the expression of Es-FABP9 and Es-FABP10 mRNA in E. sinensis was observed in hepatopancreas, gills, and hemocytes post-LPS challenge. Recombinant proteins rEs-FABP9 and rEs-FABP10 exhibited distinct bacterial binding activity and bacterial agglutination activity against Escherichia coli and Staphylococcus aureus. Furthermore, bacterial growth inhibition assays demonstrated that rEs-FABP9 responds positively to the growth inhibition of Vibrio parahaemolyticuss and S. aureus, while rEs-FABP10 responds positively to the growth inhibition of Aeromonas hydrophila and Bacillus subtilis. Coating of agarose beads with recombinant rEs-FABP9 and rEs-FABP10 dramatically enhanced encapsulation of the beads by crab hemocytes in vitro. In conclusion, the data presented here demonstrate the participation of these two lipid metabolism-related proteins in the innate immune system of E. sinensis.     

Taking insight into the gut microbiota of three spider species: No characteristic symbiont was found corresponding to the special feeding style of spiders

Microorganisms in insect guts have been recognized as having a great impact on their hosts' nutrition, health, and behavior. Spiders are important natural enemies of pests, and the composition of the gut microbiota of spiders remains unclear. Will the bacterial taxa in spiders be same as the bacterial taxa in insects, and what are the potential functions of the gut bacteria in spiders? To gain insight into the composition of the gut bacteria in spiders and their potential function, we collected three spider species, Pardosa laura, Pardosa astrigera, and Nurscia albofasciata, in the field, and high‐throughput sequencing of the 16S rRNA V3 and V4 regions was used to investigate the diversity of gut microbiota across the three spider species. A total of 23 phyla and 150 families were identified in these three spider species. The dominant bacterial phylum across all samples was Proteobacteria. Burkholderia, Ralstonia, Ochrobactrum, Providencia, Acinetobacter, Proteus, and Rhodoplanes were the dominant genera in the guts of the three spider species. The relative abundances of Wolbachia and Rickettsiella detected in N. albofasciata were significantly higher than those in the other two spider species. The relative abundance of Thermus, Amycolatopsis, Lactococcus, Acinetobacter Microbacterium, and Koribacter detected in spider gut was different among the three spider species. Biomolecular interaction networks indicated that the microbiota in the guts had complex interactions. The results of this study also suggested that at the genus level, some of the gut bacteria taxa in the three spider species were the same as the bacteria in insect guts.     

Microbiome in Intestinal Lavage Fluid May Be A Better Indicator in Evaluating The Risk of Developing Colorectal Cancer Compared with Fecal Samples

OBJECTIVE: Intestinal microbiota plays a vital role in the pathogenesis of colorectal cancer (CRC), which is crucial for assessing the risk and prognosis of CRC. Most studies regarding human gut microbiota mainly based on the feces, but the exact composition of microbiota vary significantly due to fecal composition is easily affected by many factors. We aim to evaluate whether intestinal lavage fluid (IVF) is a better substitution mirroring the gut microbiota. METHODS: We performed 16S rRNA gene analysis on fecal and IVF samples from 30 CRC patients and 25 healthy individuals, comparison in luminal (feces) / mucosal (IVF) adherent bacterial community profiles were analyzed. RESULTS: The difference between feces and IVF were observed, including the diversity and abundance of pathogenic bacteria (either in single strain or in co-occurrence pattern). IVF group shared 605 OTUs with the fecal group, but there was 94 OTUs only observed in fecal samples, while 247 OTUs were mainly existing in the IVF group. Among them, 27 vital bacterial species detected in IVF, while 10 critical species detected in fecal samples. The co-occurrence bacteria Fusobacteria Cluster and Proteobacteria Cluster 2 significantly increased in IVF than in control (P < .01), while Firmicutes Cluster 1, Firmicutes Cluster 2 and Proteobacteria Cluster 1 were markedly lower in IVF than in control (P < .001). In CRC feces, Fusobacteria Cluster was higher than in control (P < .05), but Firmicutes Cluster 1 was of substantially less abundance than in control (P < .001). Proteobacteria Cluster 2 was increased dramatically in IVF than in feces (P < .05), Firmicutes Cluster 1 were of substantially less abundance than in feces (P < .05). CONCLUSION: Pathogenic microbiota is more abundant in IVF than in feces. Microbiota of IVF may closely be related to the mucosal-associated microbial communities, which benefit from elucidating the relationship of the intestinal microbiota and CRC carcinogenesis.     

NaCl absorption across split gill lamellae of hyperregulating crabs: Transport mechanisms and their regulation

The method of mounting split lamellae of crab gills in modified Ussing chambers offers the advantage that active ion transport can be measured as short-circuit current and/or flux of radioactive tracers in relation to the epithelial surface. Moreover, further modern techniques like microelectrode impalements and current-noise analysis can be applied. The epithelium of posterior gills of Chinese crabs (Eriocheir sinensis) acclimated to fresh water actively absorbs Na⁺ and Cl⁻ independent of each other. The epithelium of the gills of shore crabs (Carcinus maenas) acclimated to brackish water actively absorbs NaCl in a coupled mode. The different osmotic gradients maintained by the two crab species are reflected in the characteristics of their gill epithelia. Chinese crabs, migrating to fresh water, have a tight gill epithelium. The gill epithelium of shore crabs, living in brackish water of at least 6–8‰ salinity, is an intermediate between tight and leaky. Regulation of NaCl absorption across the gill epithelium of Chinese crabs is achieved in a hormone-independent way by the haemolymph side osmolarity (autoregulation). Moreover, NaCl absorption is regulated by a hormonal factor of so far unknown chemical nature in the eyestalk extract which stimulates the transport rates via a cAMP-dependent signal transduction pathway, activating apical V-ATPase activity and increasing the number of open apical Na⁺ channels.     

Cross-Ocean Distribution of Rhodobacterales Bacteria as Primary Surface Colonizers in Temperate Coastal Marine Waters

Bacterial surface colonization is a universal adaptation strategy in aquatic environments. However, neither the identities of early colonizers nor the temporal changes in surface assemblages are well understood. To determine the identities of the most common bacterial primary colonizers and to assess the succession process, if any, of the bacterial assemblages during early stages of surface colonization in coastal water of the West Pacific Ocean, nonnutritive inert materials (glass, Plexiglas, and polyvinyl chloride) were employed as test surfaces and incubated in seawater off the Qingdao coast in the spring of 2005 for 24 and 72 h. Phylogenetic analysis of the 16S rRNA gene sequences amplified from the recovered surface-colonizing microbiota indicated that diverse bacteria colonized the submerged surfaces. Multivariate statistical cluster analyses indicated that the succession of early surface-colonizing bacterial assemblages followed sequential steps on all types of test surfaces. The Rhodobacterales, especially the marine Roseobacter clade members, formed the most common and dominant primary surface-colonizing bacterial group. Our current data, along with previous studies of the Atlantic coast, indicate that the Rhodobacterales bacteria are the dominant and ubiquitous primary surface colonizers in temperate coastal waters of the world and that microbial surface colonization follows a succession sequence. A conceptual model is proposed based on these findings, which may have important implications for understanding the structure, dynamics, and function of marine biofilms and for developing strategies to harness or control surface-associated microbial communities.     

Bacterial infection in the blue crab, Callinectes sapidus: course of infection and histopathology

During the summer, groups of blue crabs, Callinectes sapidus, collected in commercial crab traps in Chincoteague Bay, Virginia, often undergo heavy mortalities during the first week to 10 days in the laboratory. Gram-negative bacteria are seen in hemolymph and tissues of many of the sick and dying crabs. The bacterial infections appear to be acquired during capture and transport, suggesting that potentially pathogenic bacteria in water or on the exoskeleton may be introduced into tissues by wounding or other means during the stressful conditions suffered at that time. The pathology caused by bacterial infection includes diminution in numbers of hemocytes, reduced clotting ability of the hemolymph, and progressive formation of hemocyte aggregations with necrotic centers in the heart, arteries, and hemal sinuses and spaces. By the third day, aggregations, often with many bacteria visible in the centers, occur especially in the gills, antennal gland, and Y organ. There are large premortem plasma clots in some animals. The focal and massive necroses that occur may be due to hypoxia resulting from obstruction of hemolymph flow by cellular aggregations and plasma clots and to toxic products of necrotic cells and/or bacteria.