Physical and chemical characteristics of major aquatic ecosystems in the Victoria and Kyoga lake basins

The physical-chemical characteristics of any aquatic ecosystem include pH, conductivity, and temperature, water transparency, nutrient and the chlorophyll-a levels. Physical and chemical factors of any ecosystem determine the type and quality of flora present in it and these forms the basis on which the system operates. The elements required in largest amounts for plant productions are carbon, phosphorus, nitrogen, and silicon, which is important for diatoms as a major component of the cell wall. Nutrients may limit algal productivity in the tropics despite the high temperature there allowing rapid nutrient recycling. Nutrients most likely to be limiting African lakes are nitrogen (Talling & Talling 1965; Moss 1969; Lehman & Branstrator 1993, 1994) and phosphorus (Melack.et al l982; Kalff 1983) while silicon may limit diatom growth (Hecky & Kilham 1988). The objective of the study is to investigate the impact of physical-chemical characteristics on the distribution and abundance of organisms in the major aquatic ecosystems.

Batho-spatial distribution pattern and biomass estimate of the major demersal fishes in Lake Victoria

A generalized bottom trawl exploratory survey was carried out on Lake Victoria to: (i) define the distributional pattern and magnitude of the lakewide demersal stocks, (ii) determine the commercial potential of Haplochromis spp. and (iii) evaluate trawling as a commercial fishing technique for Lake Victoria fisheries. Preliminary results suggest that: (i) bottom trawl catches are more representative of the stocks, (ii) species diversification and fish density decrease with increasing mean depth and (iii) at least 80%of the catchable demersal ichthyomass is Haplochromis. Though bottom trawling is a much more efficient fishing technique for the Lake Victoria fisheries, bio-socio-economic consideration impose that mechanization of the fishery should better proceed in graded steps. Besides demographic and nutritional considerations indicate the necessity for rational management and increased direct human utilization of the fishery resource.

Some major unsolved aspects of the dynamics of African fisheries as related to questions of rational development and management

Studies of fish and fisheries in Africa fall in to four phases: the period of fisheries expeditions, ecological investigations, the development phase, and the period of mechanized exploitation. There is need to establish the taxonomic status and ecology of the varied components of the potentially important Haplochromis in Lake Victoria. A comprehensive study of their bionomics and life history, population structure, natality, recruitment and mortality coefficients should be undertaken. Emphasis lo be laid on the study of the ecology, especially breeding behaviour of the economically important c1upeids (Stolothrissa tanganciae and Limnothrissa miodon), in Lake Tanganyika. A comprehensive investigation into the migratory and shoaling behaviour of the Lake Victoria Tilapia to be initiated. Pre-impoundment studies to be undertaken to assess effects of hydroelectric projects of fisheries. Studies on parasites of economically important fishes to be stepped up to assess pathological effects and the biological basis for their control. The role of predators, e.g., Hydrocyon, Lates and Micropterus salmoides in commercial fish populations should be evaluated, and the knowledge gaincd used to effectively manage the fisheries in favour of the more desirable fish stocks.

A note on the commercial and sport fishing for some of the major scombroid fishes and wahoo on the Kenya coast

Commercial seerfish and wahoo catches were examined monthly during 1973 and 1974 at Malindi fish market where also fish from Ngomeni, Nambrui, Watamu and Kilifi were landed. Annual commercial catch data was compiled from Kenya Government Fisheries records at Malindi for 1973 and 1974. Sport fishing data was compiled from Angling Club log books at Bakari and outrigger clubs at Mombasa.

Treatment of Phaeodactylum tricornutum cells with papain facilitates lipid extraction.

Triacylglycerols (TAGs) from microalgae have the potential to be used for biodiesel, but several technical and economic hurdles have to be overcome. A major challenge is efficient extraction of intracellular TAGs from algae. Here we investigate the use of enzymes to deconstruct algal cell walls/membranes. We describe a rapid and simple assay that can assess the efficacy of different enzyme treatments on TAG-containing algae. By this means crude papain and bromelain were found to be effective in releasing TAGs from the diatom Phaeodactylum tricornutum, most likely because of their cysteine protease activity. Pre-treating algal biomass with crude papain enabled complete extraction of TAGs using heptane/isopropyl alcohol. Heptane as a single solvent was also effective, although complete recovery of TAG was not obtained. Economic implications of these findings are discussed, with the aim to reduce the complexity of, and energy needed in, TAG extraction.

Treatment of Phaeodactylum tricornutum cells with papain facilitates lipid extraction

Triacylglycerols (TAGs) from microalgae have the potential to be used for biodiesel, but several technical and economic hurdles have to be overcome. A major challenge is efficient extraction of intracellular TAGs from algae. Here we investigate the use of enzymes to deconstruct algal cell walls/membranes. We describe a rapid and simple assay that can assess the efficacy of different enzyme treatments on TAG-containing algae. By this means crude papain and bromelain were found to be effective in releasing TAGs from the diatom Phaeodactylum tricornutum, most likely because of their cysteine protease activity. Pre-treating algal biomass with crude papain enabled complete extraction of TAGs using heptane/isopropyl alcohol. Heptane as a single solvent was also effective, although complete recovery of TAG was not obtained. Economic implications of these findings are discussed, with the aim to reduce the complexity of, and energy needed in, TAG extraction. © 2012 Elsevier B.V.

Identification of Cj1051c as a Major determinant for the restriction barrier of Campylobacter jejuni StrainNCTC11168

Campylobacter jejuni is a leading cause of human diarrheal illness in the world, and research on it has benefitted greatly by the completion of several genome sequences and the development of molecular biology tools. However, many hurdles remain for a full understanding of this unique bacterial pathogen. One of the most commonly used strains for genetic work with C. jejuni is NCTC11168. While this strain is readily transformable with DNA for genomic recombination, transformation with plasmids is problematic. In this study, we have identified a determinant of this to be cj1051c, predicted to encode a restriction-modification type IIG enzyme. Knockout mutagenesis of this gene resulted in a strain with a 1,000-fold-enhanced transformation efficiency with a plasmid purified from a C. jejuni host. Additionally, this mutation conferred the ability to be transformed by plasmids isolated from an Escherichia coli host. Sequence analysis suggested a high level of variability of the specificity domain between strains and that this gene may be subject to phase variation. We provide evidence that cj1051c is active in NCTC11168 and behaves as expected for a type IIG enzyme. The identification of this determinant provides a greater understanding of the molecular biology of C. jejuni as well as a tool for plasmid work with strain NCTC11168. © 2012, American Society for Microbiology.

Identification and characterization of a novel envelope protein in Rana grylio virus

Viral envelope proteins have been proposed to play significant roles in virus infection and assembly. In this study, an envelope protein gene, 53R, was cloned and characterized from Rana grylio virus (RGV), a member of the family Iridoviridae. Database searches found its homologues in all sequenced iricloviruses, and sequence alignment revealed several conserved structural features shared by virus capsid or envelope proteins: a myristoylation site, two predicted transmembrane domains and two invariant cysteine residues. Subsequently, RT-PCR and Western blot detection revealed that the transcripts encoding RGV 53R and the protein itself appeared late during infection of fathead minnow cells and that their appearance was blocked by viral DNA replication inhibitor, indicating that RGV 53R is a late expression gene. Moreover, immunofluorescence localization found an association of 53R with virus factories in RGV-infected cells, and this association was further confirmed by expressing a 53R-GFP fusion protein in pEGFP-N3/53R-transfected cells. Furthermore, detergent extraction and Western blot detection confirmed that RGV 53R was associated with virion membrane. Therefore, the current data suggest that RGV 53R is a novel viral envelope protein and that it may play an important role in virus assembly. This is thought to be the first report on a viral envelope protein that is conserved in all sequenced iridoviruses.

In situ studies on the distribution patterns and dynamics of microcystins in a biomanipulation fish - bighead carp (Aristichthys nobilis)

The distribution and dynamics of microcystins in various organs of the phytoplanktivorous bighead carp were studied monthly in Lake Taihu, which is dominated by toxic cyanobacteria. There was a good agreement between LC-MS and HPLC-UV determinations. Average recoveries of spiked fish samples were 63% for MC-RR and 71% for MC-LR. The highest MC contents in intestine, liver, kidney and spleen were 85.67, 2.83, 1.70 and 1.57 mu g g(-1) DW, respectively. MCs were much higher in mid-gut walls (1.22 mu g g(-1) DW) than in hind- and fore-gut walls (0.31 and 0.18 mu g g(-1) DW, respectively), suggesting the importance of mid-gut wall as major site for MC absorption. A cysteine conjugate of MC-LR was detected frequently in kidney. Among the muscle samples analyzed, 25% were above the provisional tolerable daily intake level by WHO. Bighead is strongly resistant to microcystins and can be used as biomanipulation fish to counteract cyanotoxin contamination in eutrophic waters. (c) 2006 Elsevier Ltd. All rights reserved.

Identification and characterization of a cathepsin L-like cysteine protease from Taenia solium metacestode

Taenia solium metacestode, a larval pork tapeworm, is a causative agent of neurocysticercosis, one of the most common parasitic diseases in the human central nervous system. In this study, we identified a cDNA encoding for a cathepsin L-like cysteine protease from the T solium metacestode (TsCL-1) and characterized the biochemical properties of the recombinant enzyme. The cloned cDNA of 1216 bp encoded 339 amino acids with an approximate molecular weight of 37.6 kDa which containing a typical signal peptide sequence (17 amino acids), a pro-domain (106 amino acids), and a mature domain (216 amino acids). Sequence alignments of TsCL-1 showed low sequence similarity of 27.3-44.6 to cathepsin L-like cysteine proteases from other helminth parasites, but the similarity was increased to 35.9-55.0 when compared to mature domains. The bacterially expressed recombinant protein (rTsCL-1) did not show enzyme activity; however, the rTsCL-1 expressed in Pichia pastoris showed typical biochemical characteristics of cysteine proteases. It degraded human immunoglobulin G (IgG) and bovine serum albumin (BSA), but not collagen. Western blot analysis of the rTsCL-1 showed antigenicity against the sera from patients with cysticercosis, sparganosis or fascioliasis, but weak or no antigenicity against the sera from patients with paragonimiasis or clonorchiasis. (c) 2006 Published by Elsevier B.V.

Mitochondrial molecular clocks and the origin of the major Otocephalan clades (Pisces : Teleostei): A new insight

The Otocephala, a clade including ostariophysan and clupeomorph telcosts, represents about a quarter of total fish species diversity, with about 1000 gencra and more than 7000 species. A series of recent papers have defended that the origin of this clade and of its major groups may be significantly older than the oldest fossils of each of these groups suggest. Some of these recent papers explicitly defend a Pangean origin for some otocephalan groups Such as the Siluriformes or Cypriniformes. To know whether or not the otocephalans as a whole, and particularly the mainly freshwater, cosmopolitan otophysans could have originated before the splitting of the Pangean Supercontinent is of extreme importance, since otophysan fishes are among the most useful animal groups for the determination of historical continental relationships. In the present work we examined divergence times for each major otocephalan group by an analysis of complete mtDNA sequences, in order to investigate if these divergence times support the hypotheses advanced in recent studies. The complete mtDNA sequences of nine representative non-otocephalan fish species and of twenty-one representative otocephalan species was compared. The present study is thus, among the studies dealing with molecular divergence times of telcosts, the one in which a greater number of otocephalan species are included. The divergence times obtained support that the major otocephalan groups had a much older origin than the oldest fossil records available for these groups suggest. The origin of the Otocephala is estimated as having occurred about 282 Mya, with the origin of the Otophysi being estimated at about 251 Mya. (c) 2005 Elsevier B.V. All rights reserved.

Identification of immune genes in grass carp Ctenopharyngodon idella in response to infection of the parasitic copepod Sinergasilus major

The parasitic copepod Sinergasilus major is an important pathogen of grass carp Ctenopharyngodon idella. To understand the immune response of grass carp to the copepod infection, suppression subtractive hybridization method was employed to characterize genes up-regulation during the copepod infection in liver and gills of the fish. One hundred and twenty-two dot blot positive clones from infected subtracted library were sequenced. Searching available databases by using these nucleotide sequences revealed that 23 genes are immune-related, including known acute-phase reactants, and four novel genes encoding proteins such as source of immunodominant MHC-associated peptides (SIMP), TNF receptor-associated factor 2 binding protein (T2BP), poliovirus receptor-related protein 1 precursor, glycoprotein A repetitions predominant (GARP). The differential expression of seven immune genes, i.e. GARP, alpha-2-macroglobulin, MHC class I, C3, SIMP, T2BP, transferrin, as a result of infection was further confirmed by RT-PCR, with the up-regulation of alpha-2-macroglobulin, MHC class I, C3, SIMP and T2BP in the liver of infected fish, and down-regulation of SIMP in the gills of infected fish. The present study provides foundation for understanding grass carp immune response and candidate genes for further analysis.

Retroposon analysis of major cetacean lineages: The monophyly of toothed whales and the paraphyly of river dolphins

SINE (short interspersed element) insertion analysis elucidates contentious aspects in the phylogeny of toothed whales and dolphins (Odontoceti), especially river dolphins. Here, we characterize 25 informative SINEs inserted into unique genomic loci during evolution of odontocetes to construct a cladogram. and determine a total of 2.8 kb per taxon of the flanking sequences of these SINE loci to estimate divergence times among lineages. We demonstrate that: (i) Odontocetes are monophyletic; (ii) Ganges River dolphins, beaked whales, and ocean dolphins diverged (in this order) after sperm whales; (iii) three other river dolphin taxa, namely the Amazon, La Plata, and Yangtze river dolphins, form a monophyletic group with Yangtze River dolphins being the most basal; and (iv) the rapid radiation of extant cetacean lineages occurred some 28-33 million years B.P., in strong accord with the fossil record. The combination of SINE and flanking sequence analysis suggests a topology and set of divergence times for odontocete relationships, offering alternative explanations for several long-standing problems in cetacean evolution.