Demosponge distribution in the eastern Mediterranean: a NW–SE gradient

The purpose of this paper was to investigate patterns of demosponge distribution along gradients of environmental conditions in the biogeographical subzones of the eastern Mediterranean (Aegean and Levantine Sea). The Aegean Sea was divided into six major areas on the basis of its geomorphology and bathymetry. Two areas of the Levantine Sea were additionally considered. All available data on demosponge species numbers and abundance in each area, as well as their vertical and general geographical distribution were taken from the literature. Multivariate analysis revealed a NW–SE faunal gradient, showing an apparent dissimilarity among the North Aegean, the South Aegean and the Levantine Sea, which agrees with the differences in the geographical, physicochemical and biological characteristics of the three areas. The majority of demosponge species has been recorded in the North Aegean, while the South Aegean is closer, in terms of demosponge diversity, to the oligotrophic Levantine Sea. The number of studies in the Aegean and Levantine subareas was positively correlated with the number of species recorded within each Aegean subarea. Demosponge species with an Altanto-Mediterranean distribution prevailed in the Aegean and the Levantine. The reduced contribution of the endemic component, as compared to the western Mediterranean, is consistent with the general NW–SE decrease in the number of endemic species in the Mediterranean. Demosponge distribution at the order level showed also a NW–SE gradient, similar to that observed in the entire Atlantic–Mediterranean region, suggesting a warm water affinity. Sublittoral, circalittoral and bathyal zones were clearly distinguishable in the Aegean Sea on the basis of their sponge fauna. The total number of species was an exponential negative function of depth.     

Determinants of alpha and beta vascular plant diversity in Mediterranean island systems: the Ionian islands,Greece

The Ionian archipelago is the second largest Greek archipelago after the Aegean, but the factors driving plant species diversity in the Ionian islands are still barely known. We used stepwise multiple regressions to investigate the factors affecting plant species diversity in 17 Ionian islands. Generalized dissimilarity modelling was applied to examine variation in the magnitude and rate of species turnover along environmental gradients, as well as to assess the relative importance of geographical and climatic factors in explaining species turnover. The values of the residuals from the ISAR log₁₀‐transfomed models of native and endemic taxa were used as a measure of island floristic diversity. Area was confirmed to be the most powerful single explanatory predictor of all diversity metrics. Mean annual precipitation and temperature, as well as shortest distance to the nearest island are also significant predictors of vascular plant diversity. The island of Kalamos constitutes an important plant diversity hotspot in the Ionian archipelago. The recent formation of the islands, the close proximity to the mainland source and the relatively low dispersal filtering of the Ionian archipelago has resulted in islands with a flora principally comprising common species and a low proportion of endemics. Small islands keep a key role in conservation of plant priority sites.     

Acquisition through Horizontal Gene Transfer of Plasmid pSMA198 by Streptococcus macedonicus ACA-DC 198 Points towards the Dairy Origin of the Species

Background

Streptococcus macedonicus is an intriguing streptococcal species whose most frequent source of isolation is fermented foods similarly to Streptococcus thermophilus. However, S. macedonicus is closely related to commensal opportunistic pathogens of the Streptococcus bovis/Streptococcus equinus complex.

Methodology/Principal Findings

We analyzed the pSMA198 plasmid isolated from the dairy strain Streptococcus macedonicus ACA-DC 198 in order to provide novel clues about the main ecological niche of this bacterium. pSMA198 belongs to the narrow host range pCI305/pWV02 family found primarily in lactococci and to the best of our knowledge it is the first such plasmid to be reported in streptococci. Comparative analysis of the pSMA198 sequence revealed a high degree of similarity with plasmids isolated from Lactococcus lactis strains deriving from milk or its products. Phylogenetic analysis of the pSMA198 Rep showed that the vast majority of closely related proteins derive from lactococcal dairy isolates. Additionally, cloning of the pSMA198 ori in L. lactis revealed a 100% stability of replication over 100 generations. Both pSMA198 and the chromosome of S. macedonicus exhibit a high percentage of potential pseudogenes, indicating that they have co-evolved under the same gene decay processes. We identified chromosomal regions in S. macedonicus that may have originated from pSMA198, also supporting a long co-existence of the two replicons. pSMA198 was also found in divergent biotypes of S. macedonicus and in strains isolated from dispersed geographic locations (e.g. Greece and Switzerland) showing that pSMA198’s acquisition is not a recent event.

Conclusions/Significance

Here we propose that S. macedonicus acquired plasmid pSMA198 from L. lactis via an ancestral genetic exchange event that took place most probably in milk or dairy products. We provide important evidence that point towards the dairy origin of this species.     

Anodes Stimulate Anaerobic Toluene Degradation via Sulfur Cycling in Marine Sediments

Hydrocarbons released during oil spills are persistent in marine sediments due to the absence of suitable electron acceptors below the oxic zone. Here, we investigated an alternative bioremediation strategy to remove toluene, a model monoaromatic hydrocarbon, using a bioanode. Bioelectrochemical reactors were inoculated with sediment collected from a hydrocarbon-contaminated marine site, and anodes were polarized at 0 mV and +300 mV (versus an Ag/AgCl [3 M KCl] reference electrode). The degradation of toluene was directly linked to current generation of up to 301 mA m⁻² and 431 mA m⁻² for the bioanodes polarized at 0 mV and +300 mV, respectively. Peak currents decreased over time even after periodic spiking with toluene. The monitoring of sulfate concentrations during bioelectrochemical experiments suggested that sulfur metabolism was involved in toluene degradation at bioanodes. 16S rRNA gene-based Illumina sequencing of the bulk anolyte and anode samples revealed enrichment with electrocatalytically active microorganisms, toluene degraders, and sulfate-reducing microorganisms. Quantitative PCR targeting the α-subunit of the dissimilatory sulfite reductase (encoded by dsrA) and the α-subunit of the benzylsuccinate synthase (encoded by bssA) confirmed these findings. In particular, members of the family Desulfobulbaceae were enriched concomitantly with current production and toluene degradation. Based on these observations, we propose two mechanisms for bioelectrochemical toluene degradation: (i) direct electron transfer to the anode and/or (ii) sulfide-mediated electron transfer.     

Actin filament-organized local cortical endoplasmic reticulum aggregations in developing stomatal complexes of grasses

Endoplasmic reticulum (ER) immunolabeling in developing stomatal complexes and in the intervening cells of the stomatal rows (ICSRs) of Zea mays revealed that the cortical-ER forms distinct aggregations lining locally expanding wall regions. The polarized subsidiary cell mother cells (SMCs), displayed a cortical-ER-patch lining the wall region shared with the inducing guard cell mother cell (GMC), which disorganized during mitosis. In dividing SMCs, ER persisted in the preprophase band region and was unequally distributed in the mitotic spindle poles. The subsidiary cells (SCs) formed initially an ER-patch lining the common wall with the GMC or the young guard cells and afterwards an ER-ring in the junction of the SC wall with the neighboring ones. Distinct ER aggregations lined the ICSR wall regions shared with the SCs. The cortical-ER aggregations in stomatal cells of Z. mays were co-localized with actin filament (AF) arrays but both were absent from the respective cells of Triticum turgidum, which follow a different morphogenetic pattern. Experimental evidence showed that the interphase ER aggregations are organized by the respective AF arrays, while the mitotic ER aggregations by microtubules. These results revealed that AF and ER demarcated “cortical cytoplasmic domains” are activated below the locally expanding stomatal cell wall regions, probably via a mechanosensing mechanism triggered by the locally stressed plasmalemma/cell wall continuum. The probable role(s) of the local ER aggregations are discussed.