Protistan microbial observatory in the Cariaco Basin,Caribbean. I. Pyrosequencing vs Sanger insights into species richness

Microbial diversity and distribution are topics of intensive research. In two companion papers in this issue, we describe the results of the Cariaco Microbial Observatory (Caribbean Sea, Venezuela). The Basin contains the largest body of marine anoxic water, and presents an opportunity to study protistan communities across biogeochemical gradients. In the first paper, we survey 18S ribosomal RNA (rRNA) gene sequence diversity using both Sanger- and pyrosequencing-based approaches, employing multiple PCR primers, and state-of-the-art statistical analyses to estimate microbial richness missed by the survey. Sampling the Basin at three stations, in two seasons, and at four depths with distinct biogeochemical regimes, we obtained the largest, and arguably the least biased collection of over 6000 nearly full-length protistan rRNA gene sequences from a given oceanographic regime to date, and over 80 000 pyrosequencing tags. These represent all major and many minor protistan taxa, at frequencies globally similar between the two sequence collections. This large data set provided, via the recently developed parametric modeling, the first statistically sound prediction of the total size of protistan richness in a large and varied environment, such as the Cariaco Basin: over 36 000 species, defined as almost full-length 18S rRNA gene sequence clusters sharing over 99% sequence homology. This richness is a small fraction of the grand total of known protists (over 100 000–500 000 species), suggesting a degree of protistan endemism.     

Construction of Aspergillus nidulans strains producing enzymes of potential use in enology

Two different Aspergillus nidulans recombinant strains producing either the Aspergillus nidulans a-L-arabinofuranosidase A or a Candida molischiana b-glucosidase have been constructed. Depending on the growing conditions, the modified strains produce up to 4 or 18 times more b-glucosidase or a-L-arabinofuranosidase activity levels, respectively, than the wild type strain.     

Effect of pathogenic mutations on the structure and dynamics of Alzheimer’s Aβ42-amyloid oligomers

Converging lines of evidence suggest that soluble Aβ-amyloid oligomers play a pivotal role in the pathogenesis of Alzheimer’s disease, and present direct effectors of synaptic and cognitive dysfunction. Three pathological E22-Aβ-amyloid point mutants (E22G, E22K, E22Q) and the deletion mutant E22Δ exhibit an enhanced tendency to form prefibrillar aggregates. The present study assessed the effect of these four mutations using molecular dynamics simulations and subsequent structural and energetic analyses. Our data shows that E22 plays a unique role in wild type Aβ, since it has a destabilising effect on the oligomer structure due to electrostatic repulsion between adjacent E22 side chains. Mutations in which E22 is replaced by an uncharged residue result in higher oligomer stability. This effect is also observed to a lesser extent for the E22K mutation and is consistent with its lower pathogenicity compared to other mutants. Interestingly, deletion of E22 does not destroy the amyloid fold but is compensated by local changes in the backbone geometry that allow the preservation of a structurally important salt bridge. The finding that all mutant oligomers investigated exhibit higher internal stability than the wild type offers an explanation for the experimentally observed enhanced oligomer formation and stability.     

Biomass-size spectra in aquatic communities in shallow fluctuating Mediterranean salt marshes (Emporda wetlands, NE Spain)

The distribution of biomass among phytoplankton and free-livinginvertebrates was analysed in a shallow Mediterranean salt marshsubmitted to fluctuating water level. Among phytoplankton, biomassaccumulated in sizes dominated by mixotrophic species, indicatinga competitive advantage for these species, which also prey onother smaller primary producers. Among invertebrates, biomassaccumulated in the larger sizes, corresponding to species whichpartially exploit other nearby systems, such as the aerial environment(insects), or to those able to exploit particulated organicmatter in marsh-bed sediment (amphipods). Biomass distributionmodels developed for pelagic systems are discussed in relationto fluctuating temporary waters. The integrated spectrum approximated(r² = 0.96) a Pareto distribution with a slope of c = 1.38.Intense disturbances caused a decrease in r² and an increasein c. Under stable conditions, two different tendencies wereobserved, depending on the degree of eutrophy of the basins:higher values of c were measured in the more eutrophic basins,and lower values in the less eutrophic ones. We hypothesizethat highly irregular nutrient input could explain these differences.     

Measurement of Acetylcholine Release in Freely Moving Rats by Means of Automated Intracerebral Dialysis

The present study demonstrates the feasibility of measuring acetylcholine in perfusion samples collected by means of in vivo brain dialysis in the striata of freely moving rats. The output of the dialysis device was directly connected to an automated sample valve of a HPLC-assay system that comprises a cation exchanger, a post-column enzyme reactor, and an electrochemical detector. The presence of an acetylcholinesterase inhibitor (neostigmine) in the perfusion fluid was required for the detection of acetylcholine in the perfusate. Increasing concentrations of neostigmine induced increasing amounts of acetylcholine. Continuous perfusion with a fixed concentration (2 microM) of neostigmine resulted in gradually increasing amounts of collected acetylcholine over time although a considerable variation between successive samples exists. The brain dialysis technique was further validated by studying the effect of various drugs. Systemically administered atropine increased the output of acetylcholine, whereas the addition of tetrodotoxin to the perfusion fluid resulted in a complete disappearance of the neurotransmitter.     

Aspergillus nomius,a new aflatoxin-producing species related to Aspergillus flavus and Aspergillus tamarii

Aspergillus nomius is described and represents a new aflatoxigenic species phenotypically similar to A. flavus. Strains examined were isolated from insects and agricultural commodities. Separation from A. flavus is based on the presence of indeterminate sclerotia and a lower growth temperature. Comparisons of DNA relatedness show A. nomius to have only relatively recently evolved from A. flavus and A. tamarii.     

Plant feeding of yellow baboons (Papio cynocephalus) in Mikumi national park,Tanzania, and the relationship between seasonal feeding and immature survival

Focal-animal feeding data obtained from 64 adult baboons during a 3-year period were used together with equivalent data from 46 infants to evaluate hypotheses predicting selection for a birth peak and to study the baboon’s eclectic/selective feeding adaptation, with emphasis on differential feeding by sex, developmental trends, and seasonal use of food classes (fruit, leaf, flower, grass, etc.). The findings suggest that feeding conditions are better in the wet season than in the dry season. Despite large sexual dimorphism, estimates of total amounts eaten were virtually identical for males and females. Infants used all of the same plant-food classes as adults, but proportional differences occurred for some food classes in amounts eaten. Foods eaten proportionately less by infants were probably harder for them to obtain and process or were chosen through inexperience or for exploration. There was considerable between-year variation in amounts of food classes eaten, but the within-year standard deviations were similar, as were also the mean amounts eaten per year. An eclectic/selective feeding adaptation has the advantage of permitting long-run acquisition of adequate nutrition within a context of high feeding variation from season to season and year to year. Mixed results were obtained from hypotheses about selection for a birth peak. Although a peak occurred in the early dry season, this was not the optimal time of birth for survival. Survival was highest for individuals born in the late wet season, when the availability and probably the quality of food for lactating mothers were greatest.     

TGF-beta 1-induced inhibition of mouse mammary ductal growth: developmental specificity and characterization

TGF-beta 1, implanted into growing mouse mammary glands, was previously shown to inhibit ductal growth in an apparently normal and fully reversible manner. In this report we extend these findings to show that TGF-beta 1 inhibition is highly specific. In pregnant or hormone-treated mice, doses of TGF-beta 1 that were capable of fully inhibiting ductal elongation had little effect on the proliferation of lobuloalveolar structures. Additionally, the inhibitory action of TGF-beta 1 on ducts is epithelium-specific, resulting in cessation of DNA synthesis in the rapidly proliferating epithelium of mammary end buds, but does not inhibit DNA synthesis in the stroma surrounding the end buds. At the cellular level, transplant studies showed that TGF-beta 1 inhibited the regeneration of mammary ductal cells when implanted into mammary gland-free fat pads by suppressing the formation of new end buds, without inhibiting maintenance DNA synthesis in ductal lumenal epithelium; this observation indicates the potential of TGF-beta 1 to maintain patterning by suppressing adventitious lateral branching. The time-course of TGF-beta 1 inhibition of end buds was rapid, with cessation of DNA synthesis by 12 hr, followed by loss of the stem cell (cap cell) layer. The question of glandular exposure to TGF-beta 1 administered in EVAc implants was also investigated. Incorporation of TGF-beta 1 into EVAc was found not to degrade the hormone, while the release kinetics of the ligand from implants, its retention in the gland, and the demonstrable zone of exposure were consistent with observed inhibitory effects. These results support the hypothesis that TGF-beta 1 is a natural regulator of mammary ductal growth.