Seasonal variation in the physical properties of agar and biomass of Gracilaria sp. (chorda type) from Tosa Bay,southern Japan

Plants of Gracilaria sp.(chorda type), which grow along the coast of Uranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26 °C to 31 °C) and spring season (15.1 °C to 24.9 °C). Maximum biomass was 6952 g m^–2 in July, but gradually decreased in the autumn (30.5 °C in September to 20 °C in November) and winter (19.5 °C in December to 14.9 °C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali treatment (5% NaOH, 2 h) at three different temperatures (70, 80, and 90 °C), the agars showed gel strengths essentially that of commercial grade agars, with the best gel obtained at 80 °C. Maximum gel strength (1455 g cm^–2 of 1.5% agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spring. Gel strength was inversely correlated with agar yield, but was positively correlated with apparent viscosity. Maximum viscosity was 40 cP. in December. Gelling temperatures, pH of 1.5% agar gel, and moisture content in agars showed little variation.     

Impact of deforestation on the abundance,diversity, and richness of Culex mosquitoes in a southwest Cameroon tropical rainforest

Deforestation is a major threat to biodiversity but little data exist on how deforestation in real‐time affects the overall mosquito species community despite its known role in the transmission of diseases. We compared the abundance and diversity of Culex mosquitoes before and after deforestation along a gradient of three different anthropogenic disturbance levels in a tropical rainforest in southwestern Cameroon. The collections were conducted in unlogged forest (January, 2016), selectively logged forest (January, 2017), and within a young palm plantation (October, 2017) using net traps, sweep nets, resting traps, and dipping for immature stages in water bodies. Mosquitoes were morphologically identified to subspecies, groups, and species. A total of 2,556 mosquitoes was collected of which 1,663 (65.06%) belong to the genus Culex, (n=427 (25.68%) in the unlogged forest; n=900 (54.12%) in the selectively logged forest; and n=336 (20.2%) in the young palm plantation) with a significant difference among the habitats. Diversity and richness of mosquitoes varied significantly among habitats with the highest values found in the selectively logged forest (H=2.4; DS=0.87; S=33) and the lowest value in the unlogged forest (H=1.37; DS=0.68; S=13). The results of this study showed that deforestation affects the abundance and diversity of Culex mosquitoes and favors the invasion of anthropophilic mosquitoes. Higher mosquito abundance and diversity in the selectively logged forest than in the pristine forest is notable and some explanations for these differences are discussed.     

Association between aggregative adherence fimbriae types including putative new variants and virulence‐related genes and clump formation among aggR‐positive Escherichia coli strains isolated in Thailand and Japan

Enteroaggregative Escherichia coli (EAggEC) are an important cause of diarrhea. Four types of AAF have been identified; however, their prevalence and association with virulence properties remain unclear. E. coli strains carrying the aggR gene as EAggEC that were isolated in Japan and Thailand (n = 90) were examined for AAF subunit genes, two toxin genes (pet/astA), and clump formation. The most prevalent AAF gene was hdaA (28%), followed by aafA (20%), aggA (12%), and agg3A (4%), as well as a putative new AAF sequence (25.6%). Retention status of the toxin genes and intensities of clump formation appeared to vary according to the AAF type.     

Rate of rupture and reattachment of the band 3-ankyrin bridge on the human erythrocyte membrane

The principal bridge connecting the erythrocyte membrane to the spectrin-based skeleton is established by band 3 and ankyrin; mutations leading to reduced bridge formation or increased bridge rupture result in morphological and mechanical abnormalities. Because membrane mechanical properties are determined in part by the protein interactions that stabilize the membrane, we have evaluated the rates of rupture and reattachment of band 3-ankyrin bridges under both resting and mechanically stressed conditions. To accomplish this, we have examined the rate of ankyrin displacement from inside-out vesicles by the hexahistidine-tagged cytoplasmic domain of band 3, cdb3-(His)6 and the rate of substitution of cdb3-(His)6 into endogenous band 3-ankyrin bridges in resealed erythrocytes in the presence and absence of shear stress. We demonstrate that 1) exogenous cdb3-(His)6 displaces endogenous ankyrin from IOVs with a half-time and first order rate constant of 42 +/- 14 min and 0.017 +/- 0.0058 min(-1), respectively; 2) exogenous cdb3-(His)6 substitutes endogenous band 3 in its linkage to ankyrin in resealed cells with a half-time and first order rate constant of 12 +/- 3.6 min and 0.060 +/- 0.019 min(-1), respectively; 3) cdb3-(His)6-mediated rupture of the band 3-ankyrin bridge in resealed cells results in decreased membrane mechanical stability, decreased deformability, abnormal morphology, and spontaneous vesiculation of the cells; and 4) the above on/off rates are not significantly accelerated by mechanical shear stress. We conclude that the off rates of the band 3-ankyrin interaction are sufficiently slow to allow sustained erythrocyte deformation without loss of elasticity.     

Homogeneous Population of the Brown Alga Sargassum polycystum in Southeast Asia: Possible Role of Recent Expansion and Asexual Propagation

Southeast Asia has been known as one of the biodiversity hotspots in the world. Repeated glacial cycles during Pleistocene were believed to cause isolation of marine taxa in refugia, resulting in diversification among lineages. Recently, ocean current was also found to be another factor affecting gene flow by restricting larval dispersal in animals. Macroalgae are unique in having mode of reproduction that differs from that of animals. Our study on the phylogeographical pattern of the brown macroalga Sargassum polycystum using nuclear Internal Transcribed Spacer 2 (ITS2), plastidal RuBisCO spacer (Rub spacer) and mitochondrial cytochrome oxidase subunit-III (Cox3) as molecular markers revealed genetic homogeneity across 27 sites in Southeast Asia and western Pacific, in sharp contrast to that revealed from most animal studies. Our data suggested that S. polycystum persisted in single refugium during Pleistocene in a panmixia pattern. Expansion occurred more recently after the Last Glacial Maximum and recolonization of the newly flooded Sunda Shelf could have involved asexual propagation of the species. High dispersal ability through floating fronds carrying developing germlings may also contribute to the low genetic diversity of the species.     

Chemical composition and ethanol production potential of Thai seaweed species

This study evaluated the potential use of several Thai seaweed species for ethanol production. The high biomass of the green algae Ulva intestinalis and Rhizoclonium riparium and the red algae Gracilaria salicornia and Gracilaria tenuistipitata in an earthen pond culture led us to select these species for our study. The seaweed species were analyzed for chemical composition, resulting in ash contents of 37.62?±?0.15 % and fiber of 11.93?±?0.16 %, with the highest values in R. riparium. Low lipid values were found in all species, with the highest value (p?<?0.05) in G. salicornia (1.69?±?0.07 %) and the lowest in R. riparium (0.28?±?0.01 %) and G. tenuistipitata (0.26?±?0.01 %). The highest carbohydrate contents were found in G. tenuistipitata (54.89 %), and the lowest were in R. riparium (29.53 %). G. tenuistipitata (8.58?±?0.36 %) and U. intestinalis (8.24?±?0.28 %) had higher sulfate contents compared with G. salicornia (4.69?±?0.04 %) and R. riparium (1.97?±?0.20 %). The monosugar algal tissue components were analyzed by HPLC; rhamnose, xylose, fucose, arabinose, mannose, glucose, and galactose were used as reference sugars. Total sugar was found to be highest in G. tenuistipitata (98.21 %). Arabinose, glucose, and galactose were the main sugar components in all species. Glucose obtained from G. tenuistipitata (6.55 %) and R. riparium (6.52 %) was higher than in G. salicornia (0.27 %) and U. intestinalis (2.78 %). G. tenuistipitata fermentation gave a higher yield of ethanol (4.17?×?10^?3 g ethanol g^?1 sugars; 139.12 μg ethanol g^?1 glucose) than R. riparium (0.086?×?10^?3 g ethanol g^?1 sugars; 33.84 μg ethanol g^?1 glucose), U. intestinalis (0.074?×?10^?3 g ethanol g^?1 sugars; 9.98 μg ethanol g^?1 glucose), and G. salicornia (0.031?×?10^?3 g ethanol g^?1 sugars; 1.43 μg ethanol g^?1 glucose).     

Induction of Strain-Transcending Antibodies Against Group A PfEMP1 Surface Antigens from Virulent Malaria Parasites

Sequence diversity in pathogen antigens is an obstacle to the development of interventions against many infectious diseases. In malaria caused by Plasmodium falciparum, the PfEMP1 family of variant surface antigens encoded by var genes are adhesion molecules that play a pivotal role in malaria pathogenesis and clinical disease. PfEMP1 is a major target of protective immunity, however, development of drugs or vaccines based on PfEMP1 is problematic due to extensive sequence diversity within the PfEMP1 family. Here we identified the PfEMP1 variants transcribed by P. falciparum strains selected for a virulence-associated adhesion phenotype (IgM-positive rosetting). The parasites transcribed a subset of Group A PfEMP1 variants characterised by an unusual PfEMP1 architecture and a distinct N-terminal domain (either DBLα1.5 or DBLα1.8 type). Antibodies raised in rabbits against the N-terminal domains showed functional activity (surface reactivity with live infected erythrocytes (IEs), rosette inhibition and induction of phagocytosis of IEs) down to low concentrations (<10 µg/ml of total IgG) against homologous parasites. Furthermore, the antibodies showed broad cross-reactivity against heterologous parasite strains with the same rosetting phenotype, including clinical isolates from four sub-Saharan African countries that showed surface reactivity with either DBLα1.5 antibodies (variant HB3var6) or DBLα1.8 antibodies (variant TM284var1). These data show that parasites with a virulence-associated adhesion phenotype share IE surface epitopes that can be targeted by strain-transcending antibodies to PfEMP1. The existence of shared surface epitopes amongst functionally similar disease-associated P. falciparum parasite isolates suggests that development of therapeutic interventions to prevent severe malaria is a realistic goal.     

Classification of perA sequences and their correlation with autoaggregation in typical enteropathogenic Escherichia coli isolates collected in Japan and Thailand

Enteropathogenic Escherichia coli (EPEC) strains produce a bundle‐forming pilus (BFP) that mediates localized adherence (LA) to intestinal epithelial cells. The major structural subunit of the BFP is bundlin, which is encoded by the bfpA gene located on a large EAF plasmid. The perA gene has been shown to activate genes within the bfp operon. We analyzed perA gene polymorphism among typical (eae‐ and bfpA‐ positive) EPEC strains isolated from healthy and diarrheal persons in Japan (n= 27) and Thailand (n= 26) during the period 1995 to 2007 and compared this with virulence and phenotypic characteristics. Eight genotypes of perA were identified by heteroduplex mobility assay (HMA). The strains isolated in Thailand showed strong autoaggregation and had an intact perA, while most of those isolated in Japan showed weak or no autoaggregation, and had a truncated perA due to frameshift mutation. The degree of autoaggregation was well correlated with adherence to HEp‐2 cells, contact hemolysis and BFP expression. Our results showed that functional deficiency due to frameshift mutation and subsequent nonsense mutation in perA reduced BFP expression in typical EPEC strains isolated in Japan.     

Drug Resistance Profiles of Mycobacterium tuberculosis Complex and Factors Associated with Drug Resistance in the Northwest and Southwest Regions of Cameroon

Background

Anti-tuberculosis drug resistance continues to be a major obstacle to tuberculosis (TB) control programmes with HIV being a major risk factor in developing TB. We investigated anti-TB drug resistance profiles and the impact of socioeconomic as well as behavioural factors on the prevalence of TB and drug resistance in two regions of Cameroon with such data paucity.

Methods

This was a hospital-based study in which 1706 participants, comprising 1133 females and 573 males consecutively enrolled from selected TB and HIV treatment centres of the Northwest and Southwest regions. Demographic, clinical and self-reported risk behaviours and socioeconomic data were obtained with the consent of participants using questionnaires. Culture and drug resistance testing were performed according to standard procedures.

Results

The prevalence of resistance to at least one anti-TB drug was 27.7% and multi-drug resistance was 5.9%. Smoking, concurrent alcohol consumption and smoking, being on antiretroviral therapy for ≤ 12 months and previous household contact with TB patient were independently associated with tuberculosis prevalence, while only previous tuberculosis infection was associated with drug resistance in a univariate analysis.

Conclusion

The study showed a high prevalence of drug resistance TB in the study population with only previous TB infection associated with drug resistance in a univariate analysis. It also provides evidence in our context, of the role of alcohol and smoking in increasing the risk of developing TB, which is more likely in people living with HIV/AIDS. Therefore, it is important for public health authorities to integrate and intensify alcohol/smoking abstention interventions in TB and HIV control programs in Cameroon.