Patterns in Abundance,Cell Size and Pigment Content of Aerobic Anoxygenic Phototrophic Bacteria along Environmental Gradients in Northern Lakes

There is now evidence that aerobic anoxygenic phototrophic (AAP) bacteria are widespread across aquatic systems, yet the factors that determine their abundance and activity are still not well understood, particularly in freshwaters. Here we describe the patterns in AAP abundance, cell size and pigment content across wide environmental gradients in 43 temperate and boreal lakes of Québec. AAP bacterial abundance varied from 1.51 to 5.49 x 10⁵ cells mL^-1, representing <1 to 37% of total bacterial abundance. AAP bacteria were present year-round, including the ice-cover period, but their abundance relative to total bacterial abundance was significantly lower in winter than in summer (2.6% and 7.7%, respectively). AAP bacterial cells were on average two-fold larger than the average bacterial cell size, thus AAP cells made a greater relative contribution to biomass than to abundance. Bacteriochlorophyll a (BChla) concentration varied widely across lakes, and was not related to AAP bacterial abundance, suggesting a large intrinsic variability in the cellular pigment content. Absolute and relative AAP bacterial abundance increased with dissolved organic carbon (DOC), whereas cell-specific BChla content was negatively related to chlorophyll a (Chla). As a result, both the contribution of AAP bacteria to total prokaryotic abundance, and the cell-specific BChla pigment content were positively correlated with the DOC:Chla ratio, both peaking in highly colored, low-chlorophyll lakes. Our results suggest that photoheterotrophy might represent a significant ecological advantage in highly colored, low-chlorophyll lakes, where DOC pool is chemically and structurally more complex.     

Glutamine homeostasis and mitochondrial dynamics

Glutamine is a multifaceted amino acid that plays key roles in many metabolic pathways and also fulfils essential signaling functions. Although classified as non-essential, recent evidence suggests that glutamine is a conditionally essential amino acid in several physiological situations. Glutamine homeostasis must therefore be exquisitely regulated and mitochondria represent a major site of glutamine metabolism in numerous cell types. Glutaminolysis is mostly a mitochondrial process with repercussions in organelle structure and dynamics suggesting a tight and mutual control between mitochondrial form and cell bioenergetics. In this review we describe an updated account focused on the critical involvement of glutamine in oxidative stress, mitochondrial dysfunction and tumour cell proliferation, with special emphasis in the initial steps of mitochondrial glutamine pathways: transport into the organelle and hydrolytic deamidation through glutaminase enzymes. Some controversial issues about glutamine catabolism within mitochondria are also reviewed.     

The role of matrix metalloproteinases 2 and 9 during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide

Matrix metalloproteinases (MMPs) are implicated in a wide range of physiological and pathological processes, including morphogenesis, wound healing, angiogenesis, inflammation, and cancer. The purpose of this study was to characterize the role of MMPs as depicted by the expression of MMP-2 and MMP-9 during 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis. Male Wistar rats were distributed into three groups of 10 animals each and treated with 4-nitroquinoline 1-oxide solution at 50 ppm through their drinking water for 4, 12, and 20 weeks. Ten animals were used as control group. No histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure; however, immunoexpression of MMP-2 was noticed. The same picture occurred to MMP-9, in which positive expression was detected for this immunomarker. MMP-2 and MMP-9 showed positive expression either in pre-neoplastic lesions at 12 weeks following carcinogen exposure or in well-differentiated squamous cell carcinoma induced after 20 weeks of treatment with 4NQO. Taken together, our results support the belief that MMP-2 and MMP-9 play important role during malignant transformation and conversion of oral mucosa as assessed by immunohistochemistry.     

Identification of Bacterial Infection in Neotropical Primates

Emerging infectious diseases usually arise from wild animal populations. In the present work, we performed a screening for bacterial infection in natural populations of New World primates. The blood cell bulk DNAs from 181 individuals of four Platyrrhini genera were PCR screened for eubacterial 16S rRNA genes. Bacteria were detected and identified in 13 distinct individuals of Alouatta belzebul, Alouatta caraya, and Cebus apella monkeys from geographically distant regions in the states of Mato Grosso and Pará, Brazil. Sequence analyses showed that these Platyrrhini bacteria are closely related not only to human pathogens Pseudomonas spp. but also to Pseudomonas simiae and sheep-Acari infecting Pseudomonas spp. The identified Pseudomonas possibly represents a group of bacteria circulating in natural monkey populations.     

The comparative genomics of T-box genes.

T-box genes are defined by the presence of a conserved sequence, the so-called T-box; this codes for the T-domain, which is involved in DNA-binding and protein dimerisation. Members of this gene family have been found in all metazoans, from diploblasts to humans, and mutations in T-box gene family members in humans have been linked to several congenital disorders. Sequencing of the complete genomes of a range of invertebrate and vertebrate species has allowed the classification of individual T-box genes into five subfamilies: Brachyury, T-brain1, Tbx1, Tbx2 and Tbx6. This review will largely focus on T-box genes identified in organisms whose genomes have been fully sequenced, emphasising how comparative studies of the T-box gene family will help to reveal the roles of these genes during development and in the adult.     

Tomato pollen tube development and carbohydrate fluctuations in the autotrophic phase of growth

Ripe pollen has different soluble and insoluble carbohydrates in variable amounts. Pollen germination and pollen tube growth were studied in a tomato cultivar (Solanum lycopersicum L. cv. Platense) with atypical pollen among tomatoes due to its very low amount or absence of sucrose. In vitro assays were performed using a culture medium without carbohydrates to explore whether there is an autotrophic phase of pollen tube growth, and if there is, describe it, and to analyze the fluctuations of endogenous carbohydrates (soluble carbohydrates, starch, pectins, and callose). Pollen germination was fast (ca. 10 min) and a definite autotrophic phase was observed. Soluble carbohydrates and pectins showed the most substantial changes during this period, even after 10 min. A small amount of callose was observed in the ripe pollen and pollen tubes. Pectins were the most abundant pollen tube wall component. Pollen can be considered starchless; starch was not involved in the autotrophic phase of growth. Other types of substances must be connected with the carbohydrate metabolism, because the fluctuations of the different substances did not follow balanced stoichiometric relationships. Pollen germination and pollen tube elongation was sustained autotrophically, even though sucrose was absent and starch was negligible in pollen grains. The type of pollen reserves and the fast pollen tube formation could be selective advantages in this cultivar.     

Molecular Epidemiology of Human Oral Chagas Disease Outbreaks in Colombia

Background

Trypanosoma cruzi, the causative agent of Chagas disease, displays significant genetic variability revealed by six Discrete Typing Units (TcI-TcVI). In this pathology, oral transmission represents an emerging epidemiological scenario where different outbreaks associated to food/beverages consumption have been reported in Argentina, Bolivia, Brazil, Ecuador and Venezuela. In Colombia, six human oral outbreaks have been reported corroborating the importance of this transmission route. Molecular epidemiology of oral outbreaks is barely known observing the incrimination of TcI, TcII, TcIV and TcV genotypes.

Methodology and Principal Findings

High-throughput molecular characterization was conducted performing MLMT (Multilocus Microsatellite Typing) and mtMLST (mitochondrial Multilocus Sequence Typing) strategies on 50 clones from ten isolates. Results allowed observing the occurrence of TcI, TcIV and mixed infection of distinct TcI genotypes. Thus, a majority of specific mitochondrial haplotypes and allelic multilocus genotypes associated to the sylvatic cycle of transmission were detected in the dataset with the foreseen presence of mitochondrial haplotypes and allelic multilocus genotypes associated to the domestic cycle of transmission.

Conclusions

These findings suggest the incrimination of sylvatic genotypes in the oral outbreaks occurred in Colombia. We observed patterns of super-infection and/or co-infection with a tailored association with the severe forms of myocarditis in the acute phase of the disease. The transmission dynamics of this infection route based on molecular epidemiology evidence was unraveled and the clinical and biological implications are discussed.