The alternative sigma factor SigF is a key player in the control of secretion mechanisms in Synechocystis sp. PCC 6803

Cyanobacterial alternative sigma factors are crucial players in environmental adaptation processes, which may involve bacterial responses related to maintenance of cell envelope and control of secretion pathways. Here, we show that the Group 3 alternative sigma factor F (SigF) plays a pleiotropic role in Synechocystis sp. PCC 6803 physiology, with a major impact on growth and secretion mechanisms, such as the production of extracellular polysaccharides, vesiculation and protein secretion. Although ΔsigF growth was significantly impaired, the production of released polysaccharides (RPS) increased threefold to fourfold compared with the wild-type. ΔsigF exhibits also impairment in formation of outer-membrane vesicles (OMVs) and pili, as well as several other cell envelope alterations. Similarly, the exoproteome composition of ΔsigF differs from the wild-type both in amount and type of proteins identified. Quantitative proteomics (iTRAQ) and an in silico analysis of SigF binding motifs revealed possible targets/pathways under SigF control. Besides changes in protein levels involved in secretion mechanisms, our results indicated that photosynthesis, central carbon metabolism and protein folding/degradation mechanisms are altered in ΔsigF. Overall, this work provided new evidences about the role of SigF on Synechocystis physiology and associates this regulatory element with classical and non-classical secretion pathways.     

Direct Detection by the Xpert MTB/RIF Assay and Characterization of Multi and Poly Drug-Resistant Tuberculosis in Guinea-Bissau,West Africa

BackgroundThis study aimed to evaluate the usefulness of the Xpert MTB/RIF assay for the rapid direct detection of M. tuberculosis complex (MTBC) strains and rifampicin resistance associated mutations in a resource-limited setting such as Guinea-Bissau and its implications in the management of tuberculosis (TB) and drug resistant tuberculosis, complementing the scarce information on resistance and genotypic diversity of MTBC strains in this West African country.ConclusionsThe Xpert MTB/RIF assay was reliable for the detection of rifampicin resistant MTBC strains directly from sputum samples of patients undergoing first-line treatment for two months, being more trustworthy than the simple presence of acid-fast bacilli in the smear. Its implementation is technically simple, does not require specialized laboratory infrastructures and is suitable for resource-limited settings when a regular source of electricity and maintenance is available as well as financial and operation sustainability is guaranteed by the health authorities. A high prevalence of MDR-TB among patients at risk of MDR-TB after two months of first-line treatment was found, in support of the WHO recommendations for its use in the management of this risk group.     

Ovarian development and plasma sex steroid levels in cultured female Senegalese sole Solea senegalensis

Ovarian development was studied in cultured female Senegalese sole Solea senegalensis. Females with regressed ovaries, mainly occupied by perinucleolar oocytes, predominated throughout summer exhibiting low condition factor (K), gonadosomatic index (I(G)), and plasma 17beta-estradiol and testosterone levels. Throughout autumn and winter (ovaries at early and intermediate maturation), oocytes progressed to cortical alveoli and vitellogenic stages accompanied by increasing K, I(G), and plasma 17beta-estradiol and testosterone levels. At late winter/early spring, ovarian development reached its maximum with the predominance of females at intermediate and final maturation (the latter occupied by late vitellogenic oocytes and few early maturation oocytes) and peak values of K, I(G), and 17beta-estradiol and testosterone concentrations. Steroid levels were lower (especially testosterone) than those for naturally-spawning females, which might cause extensive atresia without final oocyte maturation (no spawning was observed). This degenerative process reduced de size of the ovary (initial and intermediate phases of regression) in association with declining K, I(G), and plasma 17beta-estradiol and testosterone levels and increasing proportions of perinucleolar oocytes. The circulating 17,20beta-dihydroxy-4-pregnen-3-one levels, the proposed maturation-inducing steroid, remained relatively constant throughout the experimental period, suggesting that oocytes were unable to respond adequately to its stimulation. We propose the inadequate seasonal thermal regime as the main cause of such dysfunction.     

Relationships between soil hydrology and forest structure and composition in the southern Brazilian Amazon

Question: Is soil hydrology an important niche‐based driver of biodiversity in tropical forests? More specifically, we asked whether seasonal dynamics in soil water regime contributed to vegetation partitioning into distinct forest types. Location: Tropical rain forest in northwestern Mato Grosso, Brazil. Methods: We investigated the distribution of trees and lianas ≥ 1 cm DBH in ten transects that crossed distinct hydrological transitions. Soil water content and depth to water table were measured regularly over a 13‐month period. Results: A detrended correspondence analysis (DCA) of 20 dominant species and structural attributes in 10 × 10 m subplots segregated three major forest types: (1) high‐statured upland forest with intermediate stem density, (2) medium‐statured forest dominated by palms, and (3) low‐statured campinarana forest with high stem density. During the rainy season and transition into the dry season, distinct characteristics of the soil water regime (i.e. hydro‐indicators) were closely associated with each vegetation community. Stand structural attributes and hydro‐indicators were statistically different among forest types. Conclusions: Some upland species appeared intolerant of anaerobic conditions as they were not present in palm and campinarana sites, which experienced prolonged periods of saturation at the soil surface. A shallow impermeable layer restricted rooting depth in the campinarana community, which could heighten drought stress during the dry season. The only vegetation able to persist in campinarana sites were short‐statured trees that appear to be well‐adapted to the dual extremes of inundation and drought.     

Influence of Several Activators on the Extracellular Laccase Activity and In vivo Decolourization of Poly R‐478 by Semi‐Solid‐State Cultures of Trametes versicolor

The effect of several laccase activity activators,such as ethanol (novel activator), veratryl alcohol, melanin production and aeration level, on the laccase production by Trametes versicolor (CBS100.29) was investigated. The microorganism was cultivated on nylon sponge, functioning as a physical support on which the mycelium was bound. The cultures with veratryl alcohol showed maximum laccase and manganese‐dependent peroxidase (MnP) activities of 238 U/l and 125 U/l, respectively. The laccase activity found is about two times higher than that attained in the control cultures. On the contrary, MnP activity did not appear to be influenced by the addition of this alcohol. Ethanol‐supplemented cultures led to maximum laccase and MnP activity levels of about 102 U/l and 101 U/l, respectively. These activities were approx. 40% lower than those achieved in the reference cultures. The decolourization of the polymeric dye Poly R‐478 by the above‐mentioned cultures was also investigated. A percentage of biological decolourization of around 90% was achieved with control and veratryl alcohol‐supplemented cultures, whereas with ethanol‐supplemented cultures a slightly lower percentage of around 85% was reached after seven days of dye incubation.     

Machine learning approach for automatic recognition of tomato-pollinating bees based on their buzzing-sounds

Bee-mediated pollination greatly increases the size and weight of tomato fruits. Therefore, distinguishing between the local set of bees–those that are efficient pollinators–is essential to improve the economic returns for farmers. To achieve this, it is important to know the identity of the visiting bees. Nevertheless, the traditional taxonomic identification of bees is not an easy task, requiring the participation of experts and the use of specialized equipment. Due to these limitations, the development and implementation of new technologies for the automatic recognition of bees become relevant. Hence, we aim to verify the capacity of Machine Learning (ML) algorithms in recognizing the taxonomic identity of visiting bees to tomato flowers based on the characteristics of their buzzing sounds. We compared the performance of the ML algorithms combined with the Mel Frequency Cepstral Coefficients (MFCC) and with classifications based solely on the fundamental frequency, leading to a direct comparison between the two approaches. In fact, some classifiers powered by the MFCC–especially the SVM–achieved better performance compared to the randomized and sound frequency-based trials. Moreover, the buzzing sounds produced during sonication were more relevant for the taxonomic recognition of bee species than analysis based on flight sounds alone. On the other hand, the ML classifiers performed better in recognizing bees genera based on flight sounds. Despite that, the maximum accuracy obtained here (73.39% by SVM) is still low compared to ML standards. Further studies analyzing larger recording samples, and applying unsupervised learning systems may yield better classification performance. Therefore, ML techniques could be used to automate the taxonomic recognition of flower-visiting bees of the cultivated tomato and other buzz-pollinated crops. This would be an interesting option for farmers and other professionals who have no experience in bee taxonomy but are interested in improving crop yields by increasing pollination.     

High SARS-CoV-2 seroprevalence in persons experiencing homelessness and shelter workers from a day-shelter in São Paulo,Brazil

Brazil presents one of the highest COVID-19 death tolls in the world. The initial SARS-CoV-2 epicenter was São Paulo city. As of 2019, the homeless population of São Paulo city was estimated at 24,344 individuals, the largest national homeless population. The present study aimed to concomitantly assess the molecular and serological prevalence and associated risk factors of SARS-CoV-2 infection in a homeless population and related shelter workers from a day-shelter. Serum samples, nasopharyngeal and oropharyngeal swabs of persons who are homeless and shelter workers collected from August 25^th to 27^th, 2020 were tested for the presence of anti-SARS-CoV-2 IgM and IgG antibodies by ELISA and SARS-CoV-2 RNA by RT-qPCR, respectively. All swab samples tested negative by RT-qPCR. Seropositivity of IgM and IgG was 5/203 (2.5%) and 111/203 (54.7%) in persons who are homeless, and 5/87 (5.7%) and 41/87 (47.1%) in shelter workers, respectively, with no statistical differences between groups. The high seroprevalence found herein indicates early environmental and urban spreading of SARS-CoV-2, associated with sociodemographic and economic vulnerability.     

Ligninolytic enzymes from corncob cultures of Phanerochaete chrysosporium under semi-solid-state conditions

The effects of adding some inducers of lignolytic activity to semi-solid-state cultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725) were investigated. The inducers assayed were veratryl alcohol and solid manganese (IV) oxide. The microorganism was cultured on corncob, which functioned both as physical support and source of nutrients. Supplementing the cultures with veratryl alcohol created the situation where manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of approximately 1,500 U/l and 200 U/l, respectively, could be attained. These activities were considerably higher than those obtained in the reference cultures (about 5 and 4-fold). In the same way, the addition of manganese (IV) oxide led to MnP and LiP activity levels of about 2,000 U/l and 300 U/l, respectively. These activities were also notably above (about 6 and 5-fold, respectively) those achieved in the reference cultures. Moreover, laccase activity (around 200 U/l) was only detected in veratryl alcohol or manganese (IV) oxide supplemented cultures.     

How integrated are behavioral and endocrine stress response traits? A repeated measures approach to testing the stress-coping style model

It is widely expected that physiological and behavioral stress responses will be integrated within divergent stress‐coping styles (SCS) and that these may represent opposite ends of a continuously varying reactive–proactive axis. If such a model is valid, then stress response traits should be repeatable and physiological and behavioral responses should also change in an integrated manner along a major axis of among‐individual variation. While there is some evidence of association between endocrine and behavioral stress response traits, few studies incorporate repeated observations of both. To test this model, we use a multivariate, repeated measures approach in a captive‐bred population of Xiphophorus birchmanni. We quantify among‐individual variation in behavioral stress response to an open field trial (OFT) with simulated predator attack (SPA) and measure waterborne steroid hormone levels (cortisol, 11‐ketotestosterone) before and after exposure. Under the mild stress stimulus (OFT), (multivariate) behavioral variation among individuals was consistent with a strong axis of personality (shy–bold) or coping style (reactive–proactive) variation. However, behavioral responses to a moderate stressor (SPA) were less repeatable, and robust statistical support for repeatable endocrine state over the full sampling period was limited to 11‐ketotestosterone. Although post hoc analysis suggested cortisol expression was repeatable over short time periods, qualitative relationships between behavior and glucocorticoid levels were counter to our a priori expectations. Thus, while our results clearly show among‐individual differences in behavioral and endocrine traits associated with stress response, the correlation structure between these is not consistent with a simple proactive–reactive axis of integrated stress‐coping style. Additionally, the low repeatability of cortisol suggests caution is warranted if single observations (or indeed repeat measures over short sampling periods) of glucocorticoid traits are used in ecological or evolutionary studies focussed at the individual level.