ALBERT

Description: We studied the effect of the quorum-sensing (QS) blockers 5-hydroxy-3[(1R)-1-hydroxypropyl]-4-methylfuran-2(5H)-one (FUR1), (5R)-3,4-dihydroxy-5-[(1S)-1,2-dihydroxyethyl]furan-2(5H)-one (FUR2) and triclosan (TRI) on the formation of bacterial biofilms, and the effect of these biofilms on the larval attachment of the polychaete Hydroides elegans and the bryozoan Bugula neritina. 14-day-old subtidal biofilms were harvested from artificial substrata and were allowed to develop in the laboratory with and without QS blockers. QS blockers inhibited the production of violacein by the QS reporter strain Chromobacterium violaceum CV026 and did not affect the metabolic activity of bacteria in multispecies biofilms. At a concentration of 10(-3) M all three tested compounds inhibited the establishment of microbial communities, but at one of 10(-4) M only FUR2 inhibited establishment. The tested QS blockers caused changes in bacterial density and bacterial community structure, as revealed by terminal restriction fragment length polymorphism and FISH. The groups most affected by QS blockers were Alphaproteobacteria, Gammaproteobacteria and the Cytophagales. Larvae of H. elegans and B. neritina avoided settling on biofilms that had developed in the presence of QS blockers. Our results suggest that QS blockers directly control the formation of multi-species biofilms, and indirectly - by means of biofilm properties - affect larval attachment on these modified biofilms.

Description: The GeoChip 4.2 gene array was employed to interrogate the microbial functional gene repertoire of sponges and seawater collected from the Red Sea and the Mediterranean. Complementary amplicon sequencing confirmed the microbial community composition characteristic of high microbial abundance (HMA) and low microbial abundance (LMA) sponges. By use of GeoChip, altogether 20 273 probes encoding for 627 functional genes and representing 16 gene categories were identified. Minimum curvilinear embedding analyses revealed a clear separation between the samples. The HMA/LMA dichotomy was stronger than any possible geographic pattern, which is shown here for the first time on the level of functional genes. However, upon inspection of individual genes, very few specific differences were discernible. Differences were related to microbial ammonia oxidation, ammonification, and archaeal autotrophic carbon fixation (higher gene abundance in sponges over seawater) as well as denitrification and radiation-stress-related genes (lower gene abundance in sponges over seawater). Except for few documented specific differences the functional gene repertoire between the different sources appeared largely similar. This study expands previous reports in that functional gene convergence is not only reported between HMA and LMA sponges but also between sponges and seawater.

Description: Following their transmission from the human to the mosquito with the bloodmeal, malaria parasites have to persevere in the mosquito midgut for approximately 1 d. During this period the parasites are highly vulnerable to factors of the mosquito midgut, including bacteria. We here aimed at determining the microbial diversity of gut bacteria of the Asian malaria vector Anophebs stephensi (Liston) during development and under different feeding regimes, including feeds on malaria parasite-infected blood. 16S rRNA and denaturing gradient gel electrophoresis analyses demonstrated an increasing reduction in the microbial diversity during mosquito development from egg to adult and identified the gram-negative bacterium Elizabethkingia meningoseptica King as the dominant species in the midgut of lab-reared male and female mosquitoes. E. meningoseptica is transmitted between generations and its predominance in the mosquito midgut was not altered by diet, when the gut microbiota was compared between sugar-fed and blood-fed female mosquitoes. Furthermore, feeds on blood infected with malaria parasites did not impact the presence of E. meningoseptica in the gut. Extracts from cultured E. meningoseptica were active against gram-positive and negative bacteria and yeast and against the blood and gametocyte transmission stages of the malaria parasite Plasmodium falciparum Welch. The antimicrobial and antiplasmodial activities of E. meningoseptica may account for its dominance in the midgut of the malaria vector.

Description: Over recent years, several PCR primers have been described to amplify genes encoding the structural subunits of ammonia monooxygenase (AMO) from ammonia-oxidizing bacteria (AOB). Most of them target amoA, while amoB and amoC have been neglected so far. This study compared the nucleotide sequence of 33 primers that have been used to amplify different regions of the amoCAB operon with alignments of all available sequences in public databases. The advantages and disadvantages of these primers are discussed based on the original description and the spectrum of matching sequences obtained. Additionally, new primers to amplify the almost complete amoCAB operon of AOB belonging to Betaproteobacteria (betaproteobacterial AOB), a primer pair for DGGE analysis of amoA and specific primers for gammaproteobacterial AOB, are also described. The specificity of these new primers was also evaluated using the databases of the sequences created during this study.

Description: Age composition and growth rates of the squid Loligo vulgaris (Lamark, 1797) were studied by examination of growth increments within statoliths of 419 specimens (mantle length, ML, ranging from 32 to 400mm). The squid were obtained by monthly sampling from the catches of commercial trawls off southern Portugal between March and September, 1993. The total number of growth increments in the mounted and ground statoliths was counted using a semi-automatic image analysis system. ML was significantly correlated with both the statolith length, TSL and the number of increments, NI. The female statolith was slightly larger than the male statolith for the same mantle size. Growth rates of individuals showed high variability with an average estimated at 34.6mm month-1 for males and 33.5mm month-1 for females. Growth in length between 70 and 280 days was best described by a power function for both sexes. The growth index of the statolith (TSL/NI) decreased with individual growth. The result may be related with the onset of sexual maturation. L. vulgaris hatched throughout the year with two distinct peaks, in spring which is the main breeding period, and in autumn. The life cycle of the L. vulgaris population on the south Portugese shelf was completed in one year.

Description: Trophodynamics of meso-zooplankton in the North Sea (NS) were assessed at a site in the southern NS, and at a shallow and a deep site in the central NS. Offshore and neritic species from different ecological niches, including Calanus spp., Temora spp. and Sagitta spp., were collected during seven cruises over 14 months from 2007 to 2008. Bulk stable isotope (SI) analysis, phospholipid-derived fatty acid (PLFA) compositions, and δ 13CPLFA data of meso-zooplankton and particulate organic matter (POM) were used to describe changes in zooplankton relative trophic positions (RTPs) and trophodynamics. The aim of the study was to test the hypothesis that the RTPs of zooplankton in the North Sea vary spatially and seasonally, in response to hydrographic variability, with the microbial food web playing an important role at times. Zooplankton RTPs tended to be higher during winter and lower during the phytoplankton bloom in spring. RTPs were highest for predators such as Sagitta sp. and Calanus helgolandicus and lowest for small copepods such as Pseudocalanus elongatus and zoea larvae (Brachyura). δ 15NPOM-based RTPs were only moderate surrogates for animals’ ecological niches, because of the plasticity in source materials from the herbivorous and the microbial loop food web. Common (16:0) and essential (eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) structural lipids showed relatively constant abundances. This could be explained by incorporation of PLFAs with δ 13C signatures which followed seasonal changes in bulk δ 13CPOM and PLFA δ 13CPOM signatures. This study highlighted the complementarity of three biogeochemical approaches for trophodynamic studies and substantiated conceptual views of size-based food web analysis, in which small individuals of large species may be functionally equivalent to large individuals of small species. Seasonal and spatial variability was also important in altering the relative importance of the herbivorous and microbial food webs.

Description: Ubiquitous SAR11 Alphaproteobacteria numerically dominate marine planktonic communities. Because they are excruciatingly difficult to cultivate, there is comparatively little known about their physiology and metabolic responses to long- and short-term environmental changes. As surface oceans take up anthropogenic, atmospheric CO2, the consequential process of ocean acidification could affect the global biogeochemical significance of SAR11. Shipping accidents or inadvertent release of chemicals from industrial plants can have strong short-term local effects on oceanic SAR11. This study investigated the effect of 2.5-fold acidification of seawater on the metabolism of SAR11 and other heterotrophic bacterioplankton along a natural temperature gradient crossing the North Atlantic Ocean, Norwegian and Greenland Seas. Uptake rates of the amino acid leucine by SAR11 cells as well as other bacterioplankton remained similar to controls despite an instant ∼50% increase in leucine bioavailability upon acidification. This high physiological resilience to acidification even without acclimation, suggests that open ocean dominant bacterioplankton are able to cope even with sudden and therefore more likely with long-term acidification effects.