Comparison of cytology and distribution of nickel in roots of Ni-hyperaccumulating and non-hyperaccumulating genotypes of Senecio coronatus

Two genotypes of Senecio coronatus (Thunb.) Harv. (Asteraceae) growing on ultramafic outcrops were identified previously: a Ni hyperaccumulator and a non-hyperaccumulator. The aim of the present study was to investigate the cytology of the roots of both genotypes, their Ni content and tissue distribution, and to ascertain whether there was a cytological basis for the differential uptake of Ni. Light and fluorescence microscopy together with histochemical methods were used to study root cytology. X-ray microanalysis by means of a nuclear microprobe—particle-induced X-ray emission (PIXE) and proton backscattering (BS) techniques—was utilized to determine the concentration and distribution of Ni and other elements. Average concentration of Ni and distribution in roots differed significantly between hyperaccumulating and non-hyperaccumulating genotypes. Ni amount in the hyperaccumulating genotype was ca. 60 times higher in the older part of the root (1,760 μg g⁻¹) and ca. 10 times higher (314 μg g⁻¹) in the younger root hair region in comparison with the equivalent parts of the non-accumulating genotype where Ni amounts were 30 μg g⁻¹. Ni distribution pattern was also different in both cases. Cytological differences were observed in the inner cortical region and exodermis of the roots. Distinct groups of specialized cells with an organelle-rich cytoplasm that produced copious numbers of spherical bodies occurred in the inner cortical region of the hyperaccumulator. Such distinct cell groups were absent from the inner cortex of the non-hyperaccumulator. Cortical cells here had a thin parietal cytoplasmic layer and produced fewer spherical bodies. In both genotypes the spherical structures were extruded from the cytoplasm into air spaces between the cells where they coalesced to form amorphous deposits, significantly larger and more abundant in the hyperaccumulator. Histochemical tests identified these deposits as a mixture of lipids, alkaloids and terpenoids. Specialized cells present in the inner cortex of the hyperaccumulating genotype demonstrated significant relative Ni depletion in comparison with the adjacent inner cortex and phloem. Casparian bands were identified in exodermal cell walls of both genotypes but the bands fluoresced more intensely in the non-accumulator suggesting differences in chemical composition and probably also a more efficient apoplastic barrier. This feature was correlated with the observed Ni distribution pattern. The highest Ni enrichment in the hyperaccumulating genotype occurred in the outer cortex; 20 times more than in the adjacent epidermis/exodermis in older portions of roots and 3 times more than in the epidermis/exodermis in younger root hair regions. In contrast, in the non-hyperaccumulating genotype, a higher concentration of nickel was found in the epidermis/exodermis compared to the outer cortex. The Ni ratio between the outer cortex and epidermis/exodermis was about 0.4 in the non-hyperaccumulator. Different cytological features exhibited by the genotypes may represent adaptive responses to the presence of high concentrations of Ni in the soil and subsequent differential uptake of Ni. Basic characteristics and elemental content of soil collected from the close vicinity of roots of two S. coronatus genotypes are reported. Wojciech Przybyłowicz on leave from the Faculty of Physics and Applied Computer Science, AGH University of Science & Technology, Kraków, Poland     

Molecular and epidemiological characterization of recurrent Mycobacterium ulcerans infections in Benin

BackgroundBuruli ulcer is a neglected tropical disease caused by Mycobacterium ulcerans, an environmental mycobacterium. Although transmission of M. ulcerans remains poorly understood, the main identified risk factor for acquiring Buruli ulcer is living in proximity of potentially contaminated water sources. Knowledge about the clinical features of Buruli ulcer and its physiopathology is increasing, but little is known about recurrence due to reinfection.Methodology/Principal findingsWe describe two patients with Buruli ulcer recurrence due to reinfection with M. ulcerans, as demonstrated by comparisons of DNA from the strains isolated at the time of the first diagnosis and at recurrence. Based on the spatial distribution of M. ulcerans genotypes in this region and a detailed study of the behavior of these two patients with respect to sources of water as well as water bodies and streams, we formulated hypotheses concerning the sites at which they may have been contaminated.Conclusions/SignificanceSecond episodes of Buruli ulcer may occur through reinfection, relapse or a paradoxical reaction. We formally demonstrated that the recurrence in these two patients was due to reinfection. Based on the sites at which the patients reported engaging in activities relating to water, we were able to identify possible sites of contamination. Our findings indicate that the non-random distribution of M. ulcerans genotypes in this region may provide useful information about activities at risk.     

Immunization of hamsters against Clostridium difficile infection using the Cwp84 protease as an antigen

Clostridium difficile is a pathogen responsible for diarrhoea and colitis, particularly after antibiotic treatment. We evaluated the C. difficile protease Cwp84, found to be associated with the S-layer proteins, as a vaccine antigen to limit the C. difficile intestinal colonization and therefore the development of the infection in a clindamycin-treated hamster model. First, we evaluated the immune response and the animal protection against death induced by several immunization routes: rectal, intragastric and subcutaneous. Antibody production was variable according to the immunization routes. In addition, serum Cwp84 antibody titres did not always correlate with animal protection after challenge with a toxigenic C. difficile strain. The best survival rate was observed with the rectal route of immunization. Then, in a second assay, we selected this immunization route to perform a larger immunization assay including a Cwp84 immunized group and a control group. Clostridium difficile intestinal colonization and survival rate, as well as the immune response were examined. Clostridium difficile hamster challenge resulted in a 26% weaker and slower C. difficile intestinal colonization in the immunized group. Furthermore, hamster survival in the Cwp84 immunized group was 33% greater than that of the control group, with a significant statistical difference.     

The Evolution of Vocal Communication: Inertia and Divergence in Two Closely Related Primates

International Journal of Primatology - Primate vocal repertoires change slowly over evolutionary time, making them good indicators of phylogenetic relatedness. Occasionally, however,...     

Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea)

Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea.     

The origins of gestures and language: history,current advances and proposed theories

Investigating in depth the mechanisms underlying human and non‐human primate intentional communication systems (involving gestures, vocalisations, facial expressions and eye behaviours) can shed light on the evolutionary roots of language. Reports on non‐human primates, particularly great apes, suggest that gestural communication would have been a crucial prerequisite for the emergence of language, mainly based on the evidence of large communication repertoires and their associated multifaceted nature of intentionality that are key properties of language. Such research fuels important debates on the origins of gestures and language. We review here three non‐mutually exclusive processes that can explain mainly great apes' gestural acquisition and development: phylogenetic ritualisation, ontogenetic ritualisation, and learning via social negotiation. We hypothesise the following scenario for the evolutionary origins of gestures: gestures would have appeared gradually through evolution via signal ritualisation following the principle of derived activities, with the key involvement of emotional expression and processing. The increasing level of complexity of socioecological lifestyles and associated daily manipulative activities might then have enabled the acquisition and development of different interactional strategies throughout the life cycle. Many studies support a multimodal origin of language. However, we stress that the origins of language are not only multimodal, but more broadly multicausal. We propose a multicausal theory of language origins which better explains current findings. It postulates that primates' communicative signalling is a complex trait continually shaped by a cost–benefit trade‐off of signal production and processing of interactants in relation to four closely interlinked categories of evolutionary and life cycle factors: species, individual and context‐related characteristics as well as behaviour and its characteristics. We conclude by suggesting directions for future research to improve our understanding of the evolutionary roots of gestures and language.     

Suffixation influences receivers' behaviour in non-human primates

Compared to humans, non-human primates have very little control over their vocal production. Nonetheless, some primates produce various call combinations, which may partially offset their lack of acoustic flexibility. A relevant example is male Campbell''s monkeys (Cercopithecus campbelli), which give one call type (‘Krak’) to leopards, while the suffixed version of the same call stem (‘Krak-oo’) is given to unspecific danger. To test whether recipients attend to this suffixation pattern, we carried out a playback experiment in which we broadcast naturally and artificially modified suffixed and unsuffixed ‘Krak’ calls of male Campbell''s monkeys to 42 wild groups of Diana monkeys (Cercopithecus diana diana). The two species form mixed-species groups and respond to each other''s vocalizations. We analysed the vocal response of male and female Diana monkeys and overall found significantly stronger vocal responses to unsuffixed (leopard) than suffixed (unspecific danger) calls. Although the acoustic structure of the ‘Krak’ stem of the calls has some additional effects, subject responses were mainly determined by the presence or the absence of the suffix. This study indicates that suffixation is an evolved function in primate communication in contexts where adaptive responses are particularly important.