Global distribution and vertical patterns of a prymnesiophyte–cyanobacteria obligate symbiosis

A marine symbiosis has been recently discovered between prymnesiophyte species and the unicellular diazotrophic cyanobacterium UCYN-A. At least two different UCYN-A phylotypes exist, the clade UCYN-A1 in symbiosis with an uncultured small prymnesiophyte and the clade UCYN-A2 in symbiosis with the larger Braarudosphaera bigelowii. We targeted the prymnesiophyte–UCYN-A1 symbiosis by double CARD-FISH (catalyzed reporter deposition-fluorescence in situ hybridization) and analyzed its abundance in surface samples from the MALASPINA circumnavigation expedition. Our use of a specific probe for the prymnesiophyte partner allowed us to verify that this algal species virtually always carried the UCYN-A symbiont, indicating that the association was also obligate for the host. The prymnesiophyte–UCYN-A1 symbiosis was detected in all ocean basins, displaying a patchy distribution with abundances (up to 500 cells ml⁻¹) that could vary orders of magnitude. Additional vertical profiles taken at the NE Atlantic showed that this symbiosis occupied the upper water column and disappeared towards the Deep Chlorophyll Maximum, where the biomass of the prymnesiophyte assemblage peaked. Moreover, sequences of both prymnesiophyte partners were searched within a large 18S rDNA metabarcoding data set from the Tara-Oceans expedition around the world. This sequence-based analysis supported the patchy distribution of the UCYN-A1 host observed by CARD-FISH and highlighted an unexpected homogeneous distribution (at low relative abundance) of B. bigelowii in the open ocean. Our results demonstrate that partners are always in symbiosis in nature and show contrasted ecological patterns of the two related lineages.     

Detecting Dysglycemia Using the 2015 United States Preventive Services Task Force Screening Criteria: A Cohort Analysis of Community Health Center Patients

BackgroundIn 2015, the United States Preventive Services Task Force (USPSTF) recommended targeted screening for prediabetes and diabetes (dysglycemia) in adults who are aged 40 to 70 y old and overweight or obese. Given increasing prevalence of dysglycemia at younger ages and lower body weight, particularly among racial/ethnic minorities, we sought to determine whether the current screening criteria may fail to identify some high-risk population subgroups.ConclusionsTargeted diabetes screening based on new USPSTF criteria may detect approximately half of adult community health center patients with undiagnosed dysglycemia and proportionately fewer racial/ethnic minorities than whites. Future research is needed to estimate the performance of these screening criteria in population-based samples.     

Functional Dentition in Brazilian Adults: An Investigation of Social Determinants of Health (SDH) Using a Multilevel Approach

Objectives

Estimate the prevalence of functional dentition among Brazilian adults using four different definitions and identify associated factors.

Methods

A cross-sectional study was conducted involving 9564 Brazilian adults aged 35–44 years who participated in the 2010 National Oral Health Survey. Data collection involved oral examinations and the administration of questionnaires. The following definitions were used: 1—WHO Functional Dentition (FDWHO: ≥ 20 teeth present); 2—well-distributed teeth (WDT: ≥ 10 teeth in each arch); 3 –Functional dentition classified by esthetics and occlusion (FD_Class5: dentitions that sequentially exhibit at least one tooth in each arch, at least 10 teeth in each arch, all maxillary and mandibular anterior teeth, three or four premolar posterior occluding pairs [POPs], and at least one molar POP bilaterally); 4—Functional dentition classified by esthetics, occlusion and periodontal status (FD_Class6: corresponds to FD_Class5 with the addition of periodontal status of all sextants in the oral cavity with, at most, shallow pockets and/or clinical attachment level of 5 mm (CPI ≤ 3 and/or CAL ≤ 1). The independent variables were individual factors (gender, self-declared skin color, schooling, monthly household income, age group, self-rated treatment need, dental pain, dental appointment in the previous 12 months and dental services) and contextual factors (Municipal Human Development Index [MHDI]), Gini coefficient, fluoridated water supply and oral health coverage). Multilevel mixed-effect Poisson regression analyses were performed.

Results

The prevalence of functional dentition based on the FDWHO, WDT, FD_Class5 and FD_Class6 definitions was 77.9%, 72.9%, 42.6% and 40.3%, respectively. Adults with ≥12 years of schooling and monthly household income from US$ 853 to 2557 had higher prevalence rates of FDWHO (PR: 1.41 and 1.10, respectively), WDT (PR: 1.58 and 1.14, respectively), FD_Class5 (PR: 2.03 and 1.27, respectively) and FD_Class6 (PR: 2.15 and 1.35, respectively). These values in the final models were adjusted for gender, self-declared skin color (FD_Class5), age group, self-rated treatment need (FDWHO, FD_Class5 and FD_Class6), dental appointment in the previous 12 months (FDWHO and WDT), dental services (FDWHO and WDT) and contextual factors. A very high MHDI and presence of fluoridated water supply were associated with higher prevalence rates of the four outcomes.

Conclusions

The incorporation of the criteria of new definitions of functional dentition led to a lower prevalence rate among Brazilian adults. Striking individual and contextual inequalities were identified with regard to the four definitions analyzed, which need to be addressed through inter-sector efforts.     

Coupling between taxonomic and functional diversity in protistan coastal communities

The study of protistan functional diversity is crucial to understand the dynamics of oceanic ecological processes. We combined the metabarcoding data of various coastal ecosystems and a newly developed trait-based approach to study the link between taxonomic and functional diversity across marine protistan communities of different size-classes. Environmental DNA was extracted and the V4 18S rDNA genomic region was amplified and sequenced. In parallel, we tried to annotate the operational taxonomic units (OTUs) from our metabarcoding dataset to 30 biological traits using published and accessible information on protists. We then developed a method to study trait correlations across protists (i.e. trade-offs) in order to build the best functional groups. Based on the annotated OTUs and our functional groups, we demonstrated that the functional diversity of marine protist communities varied in parallel with their taxonomic diversity. The coupling between functional and taxonomic diversity was conserved across different protist size classes. However, the smallest size-fraction was characterized by wider taxonomic and functional groups diversity, corroborating the idea that nanoplankton and picoplankton are part of a more stable ecological background on which larger protists and metazoans might develop.     

Biochemical characterization and structural prediction of a novel cytosolic leucyl aminopeptidase of the M17 family from Schizosaccharomyces pombe

A new leucyl aminopeptidase activity has been identified in the fission yeast Schizosaccharomyces pombe. The enzyme, which has been purified and named leucyl aminopeptidase yspII (LAP yspII), had a molecular mass of 320 and 54 kDa by gel filtration and SDS/PAGE, respectively, suggesting a homohexameric structure. The enzyme cleaved synthetic aminoacyl-4-nitroanilides at an optimum of pH 8.5, and preferred leucine and methionine as N-terminal amino acids. A clear dependence on Mn2+ concentration for activity was found, and an apparent association constant of 0.33 mM was calculated for the metal ion. Bestatin behaved as a competitive inhibitor of LAP yspII (K(i) = 0.14 microM), while chelating agents such as chloroquine, EDTA and 1,10-phenanthroline also reduced enzyme activity. A MALDI-MS analysis, followed by sequencing of two of the resulting peptides, showed that LAP yspII undoubtedly corresponds to the putative aminopeptidase C13A11.05 identified in the S. pombe genome project. The protein exhibited nearly 40% sequence identity to fungal and mammalian aminopeptidases belonging to the M17 family of metallopeptidases. Catalytic residues (Lys292 and Arg366), as well as those involved in coordination with the cocatalytic metal ions (Lys280, Asp285, Asp303, Asp362 and Glu364) and those forming the hydrophobic pocket for substrate binding (Met300, Asn360, Ala363, Thr390, Leu391, Ala483 and Met486), were perfectly conserved among all known aminopeptidases. The S. pombe enzyme is predicted to be formed two clearly distinguished domains with a well conserved C-terminal catalytic domain showing a characteristic topology of eight beta-sheets surrounded by alpha-helical segments in the form of a saddle.