Anti-parasitic activities of specific bacterial extracellular products of Streptomyces griseus SDX-4 against Ichthyophthirius multifiliis.

The ciliate Ichthyophthirius multifiliis is one of the most pathogenic parasites of fish maintained in captivity. In this study, effects of bacterial extracellular products of Streptomyces griseus SDX-4 against I. multifiliis were determined. The fermentation liquor of S. griseus was extracted successively in a separating funnel with petroleum ether, ethyl acetate, and n-butanol. In vitro assays revealed that the n-butanol extracts (NBu-E) and ethyl acetate extracts (Eto-E) of S. griseus were observed to be more effective against theronts than the other extracts with median effective concentration (EC50) values of 0.86 and 12.5 mg L(-1), respectively, and significantly reduced the survival of the tomonts and the total number of theronts released by the tomonts (P<0.05). All encysted tomonts were killed when the concentration of NBu-E was 30.0 mg L(-1). Results of in vivo test demonstrated that the number of I. multifiliis trophonts on the grass carp treated with NBu-E was markedly lower compared to the control group at 11 days after exposed to theronts (P<0.05). In the control group, 100% mortality was observed owing to heavy I. multifiliis infection at 11 days after the exposure. On the other hand, only 9.5% mortality owing to parasite infection was recorded in the groups treated with the NBu-E (30 mg L(-1)). The median lethal dose (LD50) of NBu-E for grass carp was 152.4 mg L(-1). Our results indicate that n-butanol extract of S. griseus will be useful in aquaculture for controlling I. multifiliis infections.

Phylogeography and genetic population structure of the spadenose shark (Scoliodon macrorhynchos) from the Chinese coast.

The population structure of Scoliodon macrorhynchos from the Chinese coast was investigated using the mitochondrial control region. All 19 mtDNA haplotypes from 219 sequences were identified. Relatively high average haplotype diversity (0.797) and relatively low average nucleotide diversity (0.0013) were found together with a recent and sudden population expansion. Analysis of the mismatch distributions, neutrality tests and Bayesian skyline plot showed a pattern consistent with a recent population expansion event that may have taken place during the last glacial maximum (LGM). The analysis of molecular variance (AMOVA) showed the low genetic differentiation between the populations, which may be a general feature of sharks living in coastal areas. The phylogenetic and cluster analysis of the mtDNA indicates that two putative groups (K = 2) existed in S. macrorhynchos, showing that the Taiwan Strait acted as a biogeographic barrier during major drops in the sea level in the late Pliocene epoch.

Complete mitochondrial genome of Gnathopogon taeniellus (Cypriniformes: Cyprinidae).

The complete mitochondrial genome of Gnathopogon taeniellus was first determined in this study. It is 16,596 bp in length, contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and one control region in the typical vertebrate gene order and transcriptional direction. There are total of 29 bp short overlaps and 34 bp non-coding intergenic spacers were found in the mitogenome. Overall nucleotide base composition of light strand is 29.3% A, 25.8% C, 17.9% G and 27.0% T. Two start codons (ATG and GTG) and two stop codons (TAG and TAA/T) were used in the protein-coding genes. The origin of light strand replication (OL) was identified between tRNA(Asn) and tRNA(Cys) genes and could fold a hairpin structure. The nucleotide composition of control region is 31.8% A, 20.9% C, 14.0% G and 33.3% T.

Parallel evolution of IDH2 gene in cetaceans, primates and bats.

Cetaceans and primates both have large brains that require large amounts of aerobic energy metabolism. In bats, the cost of flight makes locomotion energetically demanding. These mammalian groups may represent three independent evolutionary origins of an energy-demanding lifestyle in mammals. IDH2 encodes an enzyme in the tricarboxylic acid cycle in the mitochondrion, which plays a key role in aerobic energy metabolism. In this study, we cloned and sequenced this gene in two cetaceans, and 19 bat species, and compared the data with available primate sequences to test its evolution. We found significant signals of parallel evolution in this gene among these three groups. Parallel evolution of this gene may reflect their parallel evolution towards a higher demand for energy.

Complete mitochondrial genome of Pseudolaubuca engraulis (Pisces: Cyprinidae, Cultrinae).

The complete mitogenome of Pseudolaubuca engraulis was determined using long-distance polymerase chain reaction and sequenced by primer walking method. It is 16,612 bp in length and contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA (tRNA) genes and 1 A + T-rich control region. The gene arrangement and characterization of P. engraulis are similar to most vertebrates. The overall base composition of the heavy strand is 27.1% A, 27.5% C, 25.9% T and 19.5% G, with a slight A + T bias. The shortest tRNA-Ser2 lacks the dihydrouridine arm and is replaced with a simple loop. The termination-associated sequence and the conserved sequence blocks (1-3) are found in the control region.