An actinomycete strain, AM105T , that produces rifamycin, was isolated from mangrove sediment samples collected from the South China Sea. The strain showed closest 16S rRNA gene sequence similarity to Micromonospora matsumotoense (98.0 %). Chemotaxonomic characteristics of the isolate coincided with members of the genus Micromonospora. The value of DNA-DNA relatedness to M. matsumotoense (53.6 %) and phenotypic differences from phylogenetically related Micromonospora species indicated that this isolate belongs to a novel species, for which the name Micromonospora rifamycinica sp. nov. is proposed. The type strain is AM105 T (5CGMCC 4.2495 T 5DSM 44983 T ).Mangroves are a unique woody plant community of intertidal coasts in the tropical and subtropical zones, which are regarded as highly productive ecosystems and abode to large unexplored microbial diversity (Bashan & Holguin, 1997). Strain AM105 T was isolated from mangrove sediment samples from the South China Sea. Isolation was carried out by the standard dilution-plating technique on modified Gause inorganic agar (Gause et al., 1983), which contained 20 g soluble starch, 1 g KNO 3 , 0.5 g K 2 HPO 4 , 0.5 g MgSO 4 . 7H 2 O, 0.01 g FeSO 4 . 7H 2 O, 15 g agar, 1 l old sea water (pH 7.2-7.4). Plates were incubated for 30 days at 28 u C. A pure culture was maintained in a glycerol suspension (20 %, w/v) at 270 u C.Cultural features were observed on oatmeal agar (DSMZ medium 609), glycerol-asparagine agar (Shirling & Gottlieb, 1966), GYM agar (DSMZ medium 65), potato dextrose agar (DSMZ medium 129), Sauton's agar (Mordarska et al., 1972) and Gause inorganic agar after 7, 14 and 21 days incubation at 28 u C. Cell morphology and spore production were observed by light and scanning electron microscopy using 6-and 20-day-old cultures grown on various agar media. The ability to grow on sole carbon sources (1 %, w/v) was tested as described by Williams et al. (1983). NaCl tolerance (0-4.5 %, w/v) and temperatures (4-45 u C) for growth were tested on GYM agar. Methods and media for other physiological tests and the assays for enzymic activities were performed according to Wang (1986).For chemotaxonomic studies, the strain was grown in GYM broth in a shaking incubator at 200 r.p.m. and 28 u C for 5 days. Biomass was harvested by centrifugation and washed with distilled water. Isomers of diaminopimelic acid (DAP) and sugars were determined in whole-cell hydrolysates by TLC on microcrystalline cellulose (Wang, 1986).Genomic DNA was isolated as described by Pitcher et al. (1989). The DNA G+C content was determined using the thermal melting method (Mandel & Marmur, 1968). PCR amplification of the 16S rRNA gene and sequencing of the purified PCR product were done as described previously (Rivas et al., 2003). The sequence of isolate AM105T was aligned and compared with representative sequences of members of the genus Micromonospora obtained from GenBank using the CLUSTAL_X 1.8 program (Thompson et al., 1997). Phylogenetic analysis was performed with the MEGA version 2.1 progra...

Ammonia nitrogen has been a potential menace to aquatic animals along the coastline of China. Presently, the toxicological effects of ammonia nitrogen were mainly concentrated on fishes, while little attention has been paid to molluscs. In this study, the clam Ruditapes philippinarum was used as the target animal to investigate the toxic effects of ammonia nitrogen. Our results showed that ammonia exposure could significantly reduce the integrity of lysosomes in a dose-dependent manner. Metabolite analysis revealed that exposure doses and duration time of ammonia nitrogen could affect the variation profiles of gill metabolites. In detail, branched chain amino acids, glutamate, choline and phosphocholine were significantly decreased after a one-day exposure. Inosine and phenylalanine were found significantly increased and ATP was decreased after a three-day exposure. The changes of metabolites implied that metabolisms of muscle element, neurotransmission and cell apoptosis of gill tissues would be affected by ammonia exposure. Such inferences were supported by the diminished muscle element, decreased concentrations of catecholamines and increased apoptosis rates, respectively. Therefore, we take advantage of metabolomics integrated with conventional biological assays to find out that ammonia exposure could cause lysosome instability, metabolic disturbance, aberrant gill structures and changes to neurotransmitters, and would result in mollusk gill dysfunction in feeding, respiration and immunity.

Sequestration by metallothioneins and antioxidant defense are two kinds of important defense mechanisms employed by mollusks to minimize adverse effects caused by heavy metal contaminants in marine environment. In the present study, a novel metallothionein gene, CgMT-III, was cloned from Crassostrea gigas, consisting of eighteen conserved cysteine residues and encoding a MT III-like protein with two tandem b domains. The expression level of CgMT-III transcript induced by zinc was much higher than that induced by cadmium exposure. It suggested that CgMT-III was perhaps mainly involved in homeostatic control of zinc metabolism, which was distinct from previously identified MTs in C. gigas. Among the tested antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), SOD and GPx showed varying up-regulations in a tissuespecific manner, while CAT activities were inhibited in both gill and hepatopancreas from C. gigas exposed to heavy metals. It can be inferred that CgMT-III was mainly involved in zinc homeostasis, and CgMT-III gene together with CAT enzyme could be potential biomarkers to indicate heavy metal, especially zinc pollution in marine organisms.

Ammonia nitrogen exposure has been found to significantly increase the early apoptosis rates of gill cells, affect the contents of ATP and disturb expressions of calcium-related genes in clam Ruditapes philippinarum. Mitochondria are the centers for energy production, initiation of apoptosis and calcium signal regulation. It is hypothesized that gill mitochondrion is a target organelle for the ammonia nitrogen. Thus, ATP metabolism together with ATP-consuming functions would be interfered by ammonia exposure. In the present study, mitochondrial transmembrane potential (MTP), ATPase activities, gill functions in clearance and respiration, and histological changes were detected to characterize the effects of ammonia to the gill mitochondria in clam R. philippinarum. Results indicated that ammonia exposure led to significant decreases in MTP, Ca 2+ -ATPase activity and clearance rates. However, different concentrations of ammonia nitrogen induced different variations on H + , K + -ATPase activity and respiration rates. Histological observation revealed that subacute exposure of ammonia damaged the microstructure of gill tissues. Therefore, ammonia exposure dramatically damaged the normal structure and function of mitochondria, resulting in irreversible damage in energy formation and supply. In addition, it affected Ca 2+ and K + metabolism and inhibited food intake and respiration in clam R. philippinarum.

Coastal line is now polluted by many kinds of sewage including heavy metals discharged by intensive human activities. Cadmium is a nonessential heavy metal for organisms and can cause many kinds of adverse effect on the organisms. Suaeda salsa, a pioneer halophyte in intertidal zone of the Bohai coast, was proved to have cadmium-tolerant capacity. Given that, S. salsa was suggested as a potential coastal bio-indicator plant for cadmium contamination in the intertidal zone. Therefore, it is essential to investigate the responsive mechanism of S. salsa to cadmium since few studies focus on this subject till now. In the present study, six genes were selected to investigate the variation profiles of mRNA expression by fluorescent real-time quantitative PCR, including those involved in myo-inositol synthesis, redox reaction, salt-tolerant reaction. Results showed that cadmium exposure significantly modulate the mRNA expressions of MIPS, Nhx1, CAT2, GST, Prx Q genes. It suggested that cadmium exposure exerted an oxidative stress on S. salsa, disturbed Na+ homeostasis across membranes and interfered with the metabolism of inositol. In addition, CAT2 gene could be used as a gene marker in S. salsa to indicate cadmium pollution.