The effect of nutrient availability and temperature on chain length of the diatom, Skeletonema costatum

We determined the effects of temperature and nutrients on thechain length of a diatom, Skeletonema costatum, in batch cultureand enclosure experiments with estuarine water from San FranciscoBay, USA, using the recently developed CytoBuoy flow cytometer.Determination of the number of cells per diatom chain by CytoBuoyflow cytometer and associated software correlated well withbut was much more precise and time efficient than microscopicquantification. Increasing temperatures (from 6, 8 to 17°C)and nutrient concentrations induced high growth rates and dominanceby longer chains in a cultured S. costatum strain that was originallyacclimatized to a temperature range of 11–30°C. Similarly,a positive correlation between growth rate and chain lengthwas observed in S. costatum in batch culture and natural communitiesin enclosure experiments. Maximal chain lengths of S. costatumwere greater in natural populations than in the batch culture.Longer chains affect sinking rates and thus likely help thediatom remain suspended in the upper part of the water columnwhere physical and chemical parameters are more favorable forgrowth.     

Drivers of beta diversity of macroinvertebrate communities in tropical forest streams

1. There has recently been increasing interest in patterns of beta diversity but we still lack a comprehensive understanding of these patterns in various regions (e.g. the tropics), ecosystems (e.g. streams) and organism groups (e.g. invertebrates). 2. Our aim was to investigate the patterns of beta diversity of stream macroinvertebrates in relation to key environmental (i.e. stream size, pH and habitat degradation) and geographical variables (i.e. latitude, longitude, altitude) in a tropical region. We surveyed a total of 8–10 riffle sites in each of 34 streams (altogether 337 riffle sites were sampled) in Peninsular Malaysia to examine variation in macroinvertebrate community composition at within‐stream and among‐stream scales. 3. Based on test of homogeneity of dispersion, we found that the streams studied differed significantly in within‐stream variation in community composition (i.e. among‐site variation of within stream beta diversity). The patterns were similar based on Bray–Curtis coefficient on abundance data, Sorensen coefficient on presence–absence data and Simpson coefficient on presence–absence data. We also found that within‐stream beta diversity was significantly related to stream size, pH and latitude, with each of these variables individually accounting for around 20% of the variation in beta diversity in simple regressions, while the total variation explained by the three significant variables amounted to around 50% in multiple regressions. By contrast, habitat degradation, longitude and altitude were not significantly related to beta diversity. We also found that the factor drainage basin accounted for much of the variation in beta diversity in general linear models, suppressing the effects of environmental variables. 4. We concluded that within‐stream beta diversity is mainly related to a combination of the identity of a drainage basin and stream environmental factors. Our findings provide important background for stream environmental assessment and conservation planning by emphasising that (i) macroinvertebrate communities within streams are not homogeneous, but show considerable beta diversity, (ii) streams differ in their degree of within‐stream beta diversity, (iii) stream size and water pH should be considered in applied contexts related to within‐stream beta diversity and (iv) historical effects may be different in different drainage basins and may affect present‐day patterns of within‐stream beta diversity.     

Directional and balancing selection in human beta-defensins

Background  

In primates, infection is an important force driving gene evolution, and this is reflected in the importance of infectious disease in human morbidity today. The beta-defensins are key components of the innate immune system, with antimicrobial and cell signalling roles, but also reproductive functions. Here we examine evolution of beta-defensins in catarrhine primates and variation within different human populations.     

Isolation,Identification, Biocontrol Activity,and Plant Growth Promoting Capability of a Superior Streptomyces tricolor Strain HM10

Streptomyces is a genus with known biocontrol activity, producing a broad range of biologically active substances. Our goal was to isolate local Streptomyces species, evaluate their capacity to biocontrol the selected phytopathogens, and promote the plant growth via siderophore and indole acetic acid (IAA) production and phosphate solubilization. Eleven isolates were obtained from local soil samples in Saudi Arabia via the standard serial dilution method and identified morphologically by scanning electron microscope (SEM) and 16S rRNA amplicon sequencing. The biocontrol of phytopathogens was screened against known soil-borne fungi and bacteria. Plant growth promotion capacity was evaluated based on siderophore and IAA production and phosphate solubilization capacity. From eleven isolates obtained, one showed 99.77% homology with the type strain Streptomyces tricolor AS 4.1867, and was designated S. tricolor strain HM10. It showed aerial hyphae in SEM, growth inhibition of ten known phytopathogens in in vitro experiments, and the production of plant growth promoting compounds such as siderophores, IAA, and phosphate solubilization capacity. S. tricolor strain HM10 exhibited high antagonism against the fungi tested (i.e., Colletotrichum gloeosporides with an inhibition zone exceeding 18 mm), whereas the lowest antagonistic effect was against Alternaria solani (an inhibition zone equal to 8 mm). Furthermore, the most efficient siderophore production was recorded to strain HM8, followed by strain HM10 with 64 and 22.56 h/c (halo zone area/colony area), respectively. Concerning IAA production, Streptomyces strain HM10 was the most effective producer with a value of 273.02 μg/ml. An autochthonous strain S. tricolor HM10 should be an important biological agent to control phytopathogens and promote plant growth.     

Aspects of the bionomics of Phlebotomus sergenti sandflies from an endemic area of anthroponotic cutaneous leishmaniasis in Aleppo Governorate, Syria

Aspects of the bionomics of phlebotomine sandflies (Diptera: Psychodidae) were studied from June to November 2005 in three foci of anthroponotic cutaneous leishmaniasis (ACL) in Aleppo Governorate, Syria, where the agent Leishmania tropica (Wright) (Kinetoplastida: Trypanosomatidae) is transmitted by Phlebotomus sergenti Parrot. Syria has been designated by the World Health Organization as one of four countries in the Old World where cutaneous leishmaniasis is hyperendemic, but little is known about the biology of local vector populations. Standard collections by sticky traps showed two peaks in density, in June and late August. In total, 1840 sandflies were caught, comprising five species: Phlebotomus papatasi (Scopoli) (68.0%); P. sergenti (25.4%); Sergentomyia minuta (Rondani) (6.4%); Phlebotomus tobbi Adler & Theodor (0.1%), and Phlebotomus mascittii canaaniticus Adler & Theodor (0.1%). Similar numbers of P. sergenti were caught indoors (246 specimens) and outdoors (222), whereas P. papatasi was significantly more abundant indoors (1096 specimens) than outdoors (156) (χ² = 241, P < 0.01). In total, 212 blood-fed females were tested for host blood determination, of which 176 (83.0%) reacted with anti-species reagent. Results from 20 P. sergenti suggest that this species is an opportunistic feeder, imbibing human, ovine, avian, bovine and feline blood, although more bloodmeals were taken from humans and cattle than expected in relation to the relative proportions of potential hosts present (the forage ratio, FR). The bionomics of P. sergenti are discussed in relation to the inefficacy of control campaigns based on indoor spraying with residual insecticides that have been implemented by the Syrian Ministry of Health to control the epidemics of ACL in the Aleppo Governorate.     

Biofloc Technology: Emerging Microbial Biotechnology for the Improvement of Aquaculture Productivity

With the significant increases in the human population, global aquaculture has undergone a great increase during the last decade. The management of optimum conditions for fish production, which are entirely based on the physicochemical and biological qualities of water, plays a vital role in the prompt aquaculture growth. Therefore, focusing on research that highlights the understanding of water quality and breeding systems’ stability is very important. The biofloc technology (BFT) is a system that maximizes aquaculture productivity by using microbial biotechnology to increase the efficacy and utilization of fish feeds, where toxic materials such as nitrogen components are treated and converted to a useful product, like a protein for using as supplementary feeds to the fish and crustaceans. Thus, biofloc is an excellent technology used to develop the aquaculture system under limited or zero water exchange with high fish stocking density, strong aeration, and biota. This review is highlighted on biofloc composition and mechanism of system work, especially the optimization of water quality and treatment of ammonium wastes. In addition, the advantages and disadvantages of the BFT system have been explained. Finally, the importance of contemporary research on biofloc systems as a figure of microbial biotechnology has been emphasized with arguments for developing this system for better production of aquaculture with limited natural resources of water.Key words: biofloc, BFT, aquaculture, microbes, water quality, wastes     

Suction force variation in double-hybrid maize as a function of soil moisture

In experiments with double-hybrid maize grown in the field and in a greenhouse, we analysed the value of the suction force as related to the regime of irrigation. The results showed that the level of water supply to the plants is in good connection with the value of the suction force and the coefficient H (the relative degree of water saturation of the cells) analysed at the same time. In the case of the 2 hybrids under investigation the highest value of coefficient H was found to be between 35–48. The data indicate that the use of these two indices should take part in a physiological method for the settlement and the application of water rules in irrigation.