Project description:Analysis of B. subtilis biofilm metabolism at gene expression level. The hypothesis tested in the present study was that extracellular pH and environmental buffer influence the biofilm development. Results provide important information of the response of biofilms to changes in extracellular pH.
Project description:Arsenic metabolism is proposed to be an ancient mechanism in microbial life. Different bacteria and archaea use detoxification processes to grow under high arsenic concentration. Some of them are also able to use arsenic as a bioenergetic substrate in either anaerobic arsenate respiration or chemolithotrophic growth on arsenite. However, among the archaea, bioenergetic arsenic metabolism has only been found in the Crenarchaeota phylum. Here we report the discovery of haloarchaea (Euryarchaeota phylum) biofilms forming under the extreme environmental conditions such as high salinity, pH and arsenic concentration at 4589 m above sea level inside a volcano crater in Diamante Lake, Argentina. Metagenomic analyses revealed a surprisingly high abundance of genes used for arsenite oxidation (aioBA) and respiratory arsenate reduction (arrCBA) suggesting that these haloarchaea use arsenic compounds as bioenergetics substrates. We showed that several haloarchaea species, not only from this study, have all genes required for these bioenergetic processes. The phylogenetic analysis of aioA showed that haloarchaea sequences cluster in a novel and monophyletic group, suggesting that the origin of arsenic metabolism in haloarchaea is ancient. Our results also suggest that arsenite chemolithotrophy likely emerged within the archaeal lineage. Our results give a broad new perspective on the haloarchaea metabolism and shed light on the evolutionary history of arsenic bioenergetics.
Project description:Biofilm formation is an important virulence trait of the pathogenic yeast Candida albicans. We have combined gene overexpression, strain barcoding and microarray profiling to screen a library of 531 C. albicans conditional overexpression strains (~10% of the genome) for genes affecting biofilm development in mixed-population experiments. The overexpression of 16 genes increased strain occupancy within a multi-strain biofilm, whereas overexpression of 4 genes decreased it. The set of 16 genes was significantly enriched for those encoding predicted glycosylphosphatidylinositol (GPI)-modified proteins, namely Ihd1/Pga36, Phr2, Pga15, Pga19, Pga22, Pga32, Pga37, Pga42 and Pga59; eight of which have been classified as pathogen-specific. Validation experiments using either individually- or competitively-grown overexpression strains revealed that the contribution of these genes to biofilm formation was variable and stage-specific. Deeper functional analysis of PGA59 and PGA22 at a single-cell resolution using atomic force microscopy showed that overexpression of either gene increased C. albicans ability to adhere to an abiotic substrate. However, unlike PGA59, PGA22 overexpression led to cell cluster formation that resulted in increased sensitivity to shear forces and decreased ability to form a single-strain biofilm. Within the multi-strain environment provided by the PGA22-non overexpressing cells, PGA22-overexpressing cells were protected from shear forces and fitter for biofilm development. Ultrastructural analysis, genome-wide transcript profiling and phenotypic analyses in a heterologous context suggested that PGA22 affects cell adherence through alteration of cell wall structure and/or function. Taken together, our findings reveal that several novel predicted GPI-modified proteins contribute to the cooperative behaviour between biofilm cells and are important participants during C. albicans biofilm formation. Moreover, they illustrate the power of using signature tagging in conjunction with gene overexpression for the identification of novel genes involved in processes pertaining to C. albicans virulence.
Project description:Light is one of the main environmental cues that affects the physiology and behavior of many organisms. The effect of light on genome-wide transcriptional regulation has been well-studied in green algae and plants, but not in red algae. Cyanidioschyzon merolae is used as a model red algae, and is suitable for studies on transcriptomics because of its compact genome with a relatively small number of genes. In addition, complete genome sequences of the nucleus, mitochondrion, and chloroplast of this organism have been determined. Together, these attributes make C. merolae an ideal model organism to study the response to light stimuli at the transcriptional and the systems biology levels. Previous studies have shown that light significantly affects cell signaling in this organism, but there are no reports on its blue light- and red light-mediated transcriptional responses. We investigated the direct effects of blue and red light at the transcriptional level using RNA-seq. Blue and red light were found to regulate 35% of the total genes in C. merolae. Blue light affected the transcription of genes involved protein synthesis while red light specifically regulated the transcription of genes involved in photosynthesis and DNA repair. Blue or red light regulated genes involved in carbon metabolism and pigment biosynthesis. Overall, our data showed that red and blue light regulate the majority of the cellular, cell division, and repair processes in C. merolae.
Project description:Light is one of the main environmental cues that affects the physiology and behavior of many organisms. The effect of light on genome-wide transcriptional regulation has been well-studied in green algae and plants, but not in red algae. Cyanidioschyzon merolae is used as a model red algae, and is suitable for studies on transcriptomics because of its compact genome with a relatively small number of genes. In addition, complete genome sequences of the nucleus, mitochondrion, and chloroplast of this organism have been determined. Together, these attributes make C. merolae an ideal model organism to study the response to light stimuli at the transcriptional and the systems biology levels. Previous studies have shown that light significantly affects cell signaling in this organism, but there are no reports on its blue light- and red light-mediated transcriptional responses. We investigated the direct effects of blue and red light at the transcriptional level using RNA-seq. Blue and red light were found to regulate 35% of the total genes in C. merolae. Blue light affected the transcription of genes involved protein synthesis while red light specifically regulated the transcription of genes involved in photosynthesis and DNA repair. Blue or red light regulated genes involved in carbon metabolism and pigment biosynthesis. Overall, our data showed that red and blue light regulate the majority of the cellular, cell division, and repair processes in C. merolae.
Project description:Biofilm formation is an important virulence trait of the pathogenic yeast Candida albicans. Large-scale genetics strategies aimed at identifying genes involved in biofilm development are hampered by lack of a complete sexual cycle in this diploid yeast in addition to the tedious generation of homozygous gene-deletion mutants. Gene overexpression is an attractive alternative strategy for large-scale phenotypic analyses and gene-function studies. We combined gene overexpression, strain barcoding and microarray profiling to screen a library of 531 C. albicans conditional overexpression strains (~10% of the genome) for genes affecting i) planktonic cell fitness and ii) biofilm development in mixed-population experiments. We found 5 genes whose overexpression affects planktonic strain fitness, including RAD53, RAD51, PIN4, orf19.2781, all encoding (or predicted to encode) regulators of DNA-damage response or cell-cycle progression and SFL2, involved in filamentous growth. We identified 16 and 4 genes (out of 531) whose overexpression respectively increases and decreases strain occupancy within the multi-strain biofilm. Strikingly, strains with increased abundance in the multi-strain biofilm were significantly enriched for genes encoding cell wall proteins (10 genes), including the glycosylphosphatidylinositol (GPI)-anchored proteins Pga15, Pga19, Pga22, Pga59, Pga32 and Pga41. Data validation experiments using either individually- or competitively-grown overexpression and/or the respective knock-out strains revealed that the identified genes differently contribute to biofilm formation during specific stages of biofilm development, including increased or decreased substrate adherence (IHD1, PGA32, PGA37, PGA15, PGA22, PGA59 and PGA19) or biofilm biomass growth and cohesion (PGA15, PGA59 and PGA22). In line with the hypothesis that cell wall genes contribute to biofilm development, we show that strains overexpressing PGA15 or PGA22 display altered cell wall structures. Our study reveals that cell wall proteins are important actors during C. albicans biofilm formation and illustrates the powerful use of signature tagging in conjunction with gene overexpression for the identification of genes involved in processes pertaining to C. albicans virulence. A total of 8 samples are included in this study. For fitness profiling of planktonic cells, 2 biological replicates were analyzed (samples Pool_Fitness_planktonic_rep1 and Pool_Fitness_planktonic_rep2). For quantification of strain abundance during biofilm formation, 6 biological replicates were analyzed (Pool_Biofilm_rep1, Pool_Biofilm_rep2, Pool_Biofilm_rep3, Pool_Biofilm_rep4, Pool_Biofilm_rep5, Pool_Biofilm_rep6). Genomic DNA was purified and used as template to PCR-amplify barcodes, which were then used as probes for microarray hybridization. This experiment was done twice independently. For quantification of strain abundance during multi-strain biofilm formation, strain pools were grown in minimal GHAUM medium with or without doxycycline, each inoculum was then diluted to an OD600 of 1 in fresh minimal GHAUM medium with or without doxycycline and left at room temperature for 30 min, to allow further overexpression. Plastic slides (ThermanoxM-bM-^DM-"; Nunc) were immersed in the inoculum for 30 min at room temperature to allow adhesion of cells to the plastic substrate. The plastic slides were then transferred to the glass vessel of a 40-mL incubation chamber. This vessel has two glass tubes inserted to drive the entry of medium and air, while used medium is evacuated through a third tube. The flow of medium is controlled by a recirculation pump (IsmatecM-BM-.) set at 0.6 mL.min-1 and pushed by pressured air supplied at 105 Pa, conditions minimizing planktonic phase growth and promoting biofilm formation. The chambers with the plastic substrate were incubated at 37C and biofilms were grown for 40h followed by genomic DNA extraction, barcode amplification and differential labeling (dox-treated samples with Cy5, untreated samples with Cy3) and hybridization to barcode microarrays.
Project description:Transcriptional profiling of Escherichia coli in the biofilm mode of growth. A comparison of the transcriptional profiles of the biofilm interior and perimeter.
Project description:Microarrays offer a comprehensive tool for a system-wide analysis of cell functioning based on the simultaneous detection of the activity of thousands of genes. While transcriptome analyses are usually related with the study of gene expression and regulation within single species in laboratory experiments or environmental samples, in the present study, the possibility of studying gene expression in river biofilm communities was explored. To this aim a Functional Gene array (FGA), based on consensus sequences from genes of key physiological processes, was designed including 83 functional genes chosen to reflect several essential biochemical pathways and specific stress response pathways. Probes of these genes were designed from consensus sequences from up to 6 microalgal species (diatoms and chlorophytes). Furthermore, species specific probes were included resulting in 1556 unique oligonucleotide probes for 83 different genes. RNA extracted from Chlamydomonas reinhardtii, Scenedesmus vacuolatus and multi-species biofilms was then hybridized to oligonucleotide arrays at different hybridization temperatures (55, 60 and 65ºC). Signal intensity was affected by sequence divergence but results showed that hybridisation temperature of 55ºC allowed a good compromise between cross-hybridization and specificity. Due to the limited number of probes and available sequence information the designed FGAs is at present particularly useful for the comparison of similar biofilms exposed to different conditions in laboratory experimental studies. Nine samples were used, three were extracted from biofilm communities and hybridized at 55, 60 and 65 ºC, respectively; three were extracted from Scenedesmus vacuolatus and hybridized at 55, 60 and 65 ºC, respectively; and the three last ones were extracted from Chlamydomonas reinhardtii and hybridized at 55, 60 and 65 ºC