A network-based approach to identify substrate classes of bacterial glycosyltransferases

Integrated transcriptomic analysis of human induced pluripotent stem cell-derived osteogenic differentiation reveals a regulatory role of KLF16

Osteogenic differentiation is essential for bone development, metabolism, and repair; however, the underlying regulatory relationships among genes remain poorly understood. To elucidate the transcriptomic changes and identify novel regulatory genes involved in osteogenic differentiation, we differentiated mesenchymal stem cells (MSCs) derived from 20 human iPSC lines into preosteoblasts (preOBs) and osteoblasts (OBs). We then performed transcriptome profiling of MSCs, preOBs and OBs. The iPSC-derived MSCs and OBs showed similar transcriptome profiles to those of primary human MSCs and OBs, respectively. Differential gene expression analysis revealed global changes in the transcriptomes from MSCs to preOBs, and then to OBs, including the differential expression of 840 genes encoding transcription factors (TFs). TF regulatory network analysis uncovered a network comprising 451 TFs, organized into five interactive modules. Multiscale embedded gene co-expression network analysis (MEGENA) identified gene co-expression modules and key network regulators (KNRs). From these analyses, KLF16 emerged as an important TF in osteogenic differentiation. We demonstrate that overexpression of Klf16 in vitro inhibited osteogenic differentiation and mineralization, while Klf16 +/- mice exhibited increased bone mineral density, trabecular number, and cortical bone area. Our study underscores the complexity of osteogenic differentiation and identifies novel regulatory genes such as KLF16, which plays an inhibitory role in osteogenic differentiation both in vitro and in vivo.

Prokrustean Graph: A substring index for rapid k-mer size analysis

Despite the widespread adoption of k-mer-based methods in bioinformatics, understanding the influence of k-mer sizes remains a persistent challenge. Selecting an optimal k-mer size or employing multiple k-mer sizes is often arbitrary, application-specific, and fraught with computational complexities. Typically, the influence of k-mer size is obscured by the outputs of complex bioinformatics tasks, such as genome analysis, comparison, assembly, alignment, and error correction. However, it is frequently overlooked that every method is built above a well-defined k-mer-based object like Jaccard Similarity, de Bruijn graphs, k-mer spectra, and Bray-Curtis Dissimilarity. Despite these objects offering a clearer perspective on the role of k-mer sizes, the dynamics of k-mer-based objects with respect to k-mer sizes remain surprisingly elusive. This paper introduces a computational framework that generalizes the transition of k-mer-based objects across k-mer sizes, utilizing a novel substring index, the Prokrustean graph. The primary contribution of this framework is to compute quantities associated with k-mer-based objects for all k-mer sizes, where the computational complexity depends solely on the number of maximal repeats and is independent of the range of k-mer sizes. For example, counting vertices of compacted de Bruijn graphs for k = 1 , … , 100 can be accomplished in mere seconds with our substring index constructed on a gigabase-sized read set. Additionally, we derive a space-efficient algorithm to extract the Prokrustean graph from the Burrows-Wheeler Transform. It becomes evident that modern substring indices, mostly based on longest common prefixes of suffix arrays, inherently face difficulties at exploring varying k-mer sizes due to their limitations at grouping co-occurring substrings. We have implemented four applications that utilize quantities critical in modern pangenomics and metagenomics. The code for these applications and the construction algorithm is available at https://github.com/KoslickiLab/prokrustean.

Mating and ecdysone signaling modify growth, metabolism, and digestive efficiency in the female Drosophila gut

Adaptive changes in organ size and physiology occur in most adult animals, but how these changes are regulated is not well understood. Previous research found that mating in Drosophila females drives not only increases in gut size and stem cell proliferation but also alters feeding behavior, intestinal gene expression, and whole-body lipid storage, suggesting altered gut metabolism. Here, we show that mating dramatically alters female gut metabolism and digestive function. In addition to promoting a preference for a high-protein diet, mating also altered levels of TCA cycle intermediates and fatty acids in the gut, increased total gut lipids and protein, reduced relative carbohydrate levels, and enhanced the efficiency of protein digestion relative to carbohydrate digestion. The expression of genes that mediate each of these metabolic processes was similarly altered. In addition, we noted the mating-dependent downregulation of oxidative stress response and autophagy genes. Mating-dependent increases in ecdysone signaling played an important role in re-programming many, but not all, of these changes in the female gut. This study contributes to our understanding of how steroid signaling alters gut physiology to adapt to the demands of reproduction.

Rapid speciation in the holopelagic ctenophore Mnemiopsis following glacial recession

Understanding how populations diverge is one of the oldest and most compelling questions in evolutionary biology. An in depth understanding of how this process operates in planktonic marine animals, where barriers for gene flow are seemingly absent, is critical to understanding the past, present, and future of ocean life. Mnemiopsis plays an important ecological role in its native habitat along the Atlantic coast of the Americas and is highly destructive in its non-native habitats in European waters. Although historical literature described three species of Mnemiopsis, the lack of stable morphological characters has led to the collapse of this group into a single species, Mnemiopsis leidyi. We generate high-quality reference genomes and use a whole-genome sequencing approach to reveal that there are two species of Mnemiopsis along its native range and show that historical divergence between the two species coincides with historical glacial melting. We define a hybridization zone between species and highlight that environmental sensing genes likely contribute to the invasive success of Mnemiopsis. Overall, this study provides insights into the fundamental question of how holopelagic species arise without clear barriers to gene flow and sheds light on the genomic mechanisms important for invasion success in a highly invasive species.

moPepGen: Rapid and Comprehensive Identification of Non-canonical Peptides

Gene expression is a multi-step transformation of biological information from its storage form (DNA) into functional forms (protein and some RNAs). Regulatory activities at each step of this transformation multiply a single gene into a myriad of proteoforms. Proteogenomics is the study of how genomic and transcriptomic variation creates this proteomic diversity, and is limited by the challenges of modeling the complexities of gene-expression. We therefore created moPepGen, a graph-based algorithm that comprehensively generates non-canonical peptides in linear time. moPepGen works with multiple technologies, in multiple species and on all types of genetic and transcriptomic data. In human cancer proteomes, it enumerates previously unobservable noncanonical peptides arising from germline and somatic genomic variants, noncoding open reading frames, RNA fusions and RNA circularization. By enabling efficient detection and quantitation of previously hidden proteins in both existing and new proteomic data, moPepGen facilitates all proteogenomics applications. It is available at: https://github.com/uclahs-cds/package-moPepGen.

TML1 AND TML2 SYNERGISTICALLY REGULATE NODULATION AND AFFECT ARBUSCULAR MYCORRHIZA IN MEDICAGO TRUNCATULA

Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plant's need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of Nodulation (AON) and Autoregulation of Mycorrhization (AOM) both negatively regulate their respective processes and share multiple components - plants that make too many nodules usually have higher AM fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus . M. truncatula has two sequence homologs: Mt TML1 and Mt TML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR-Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in Mt TML1 or Mt TML2 produced 2-3 times the nodules of wild-type plants whereas plants containing mutations in both genes displayed a synergistic effect, forming 20x more nodules compared to wild type plants. Examination of expression and heterozygote effects suggest genetic compensation may play a role in the observed synergy. Plants with mutations in both TMLs only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of Mt TML1 and Mt TML2 in M. truncatula symbiosis with beneficial microbes.

Clean-label alternatives for food preservation: An emerging trend

Consumer demand for natural or 'clean-label' food ingredients has risen over the past 50 years and continues growing. Consumers have become more aware of their health and, therefore, insist on transparency in the list of ingredients. Preservatives are the most crucial food additives, ensuring food safety and security. Despite tremendous technological advancements, food preservation remains a significant challenge worldwide, primarily because most are synthetic and non-biodegradable. As a result, the food industry is placing more value on microbiota and other natural sources for bio-preservation, leading to the substitution of conventional processing and chemical preservatives with natural alternatives to ensure 'clean-label.' General Standard for Food Additives (GSFA) includes some of these 'clean-label' options in its list of additives. However, they are very rarely capable of replacing a synthetic preservative on a 'one-for-one' basis, putting pressure on researchers to decipher newer, cleaner, and more economical alternatives. Academic and scientific research has led to the discovery of several plant, animal, and microbial metabolites that may function as effective bio-preservatives. However, most have not yet been put in the market or are under trial. Hence, the present review aims to summarise such relevant and potential metabolites with bio-preservative properties comprehensively. This article will help readers comprehend recent innovations in the 'clean-label' era, provide informed choices to consumers, and improve the business of regulatory approvals.

Demequina capsici sp. nov., a novel plant growth-promoting actinomycete isolated from the rhizosphere of bell pepper (Capsicum annuum)

Demequina, commonly found in coastal and marine environments, represents a genus of Actinomycetes. In this study, strains Demequina PMTSA13T and OYTSA14 were isolated from the rhizosphere of Capsicum annuum, leading to the discovery of a novel species, Demequina capsici. Bacteria play a significant role in plant growth, yet there have been no reports of the genus Demequina acting as plant growth-promoting bacteria (PGPB). Comparative genomics analysis revealed ANI similarity values of 74.05-80.63% for PMTSA13T and 74.02-80.54% for OYTSA14, in comparison to various Demequina species. The digital DNA-DNA hybridization (dDDH) values for PMTSA13T ranged from 19 to 39%, and 19.1-38.6% for OYTSA14. Genome annotation revealed the presence of genes associated with carbohydrate metabolism and transport, suggesting a potential role in nutrient cycling and availability for plants. These strains were notably rich in genes related to 'carbohydrate metabolism and transport (G)', according to their Cluster of Orthologous Groups (COG) classification. Additionally, both strains were capable of producing auxin (IAA) and exhibited enzymatic activities for cellulose degradation and catalase. Furthermore, PMTSA13T and OYTSA14 significantly induced the growth of Arabidopsis thaliana seedlings primarily attributed to their capacity to produce IAA, which plays a crucial role in stimulating plant growth and development. These findings shed light on the potential roles of Demequina strains in plant-microbe interactions and agricultural applications. The type strain is Demequina capsici PMTSA13T (= KCTC 59028T = GDMCC 1.4451T), meanwhile OYTSA14 is identified as different strains of Demequina capsici.

ADBP-1 regulates ADR-2 nuclear localization to control editing substrate selection

Adenosine-to-inosine (A-to-I) RNA editing, catalyzed by ADAR enzymes, is a prevalent and conserved RNA modification. While A-to-I RNA editing is essential in mammals, in Caenorhabditis elegans , it is not, making them invaluable for RNA editing research. In C. elegans , ADR-2 is the sole catalytic A-to-I editing enzyme, and ADR-1 is an RNA editing regulator. ADAR localization is well-studied in humans but not well-established in C. elegans . In this study, we examine the cellular and tissue-specific localization of ADR-2. We show that while ADR-2 is present in most cells in the embryo, at later developmental stages, its expression is both tissue- and cell-type-specific. Additionally, both ADARs are mainly in the nucleus. ADR-2 is adjacent to the chromosomes during the cell cycle. We show that the nuclear localization of endogenous ADR-2 depends on ADBP-1, not ADR-1. In adbp-1 mutant worms, ADR-2 is mislocalized, while ADR-1 is not, leading to decreased editing levels and de-novo editing, mostly in exons, suggesting that ADR-2 is also functional in the cytoplasm. Besides, mutated ADBP-1 affects gene expression. Furthermore, we show that ADR-2 targets adenosines with different surrounding nucleotides in exons and introns. Our findings indicate that ADR-2 cellular localization is highly regulated and affects its function.

CoRAL accurately resolves extrachromosomal DNA genome structures with long-read sequencing

Extrachromosomal DNA (ecDNA) is a central mechanism for focal oncogene amplification in cancer, occurring in approximately 15% of early stage cancers and 30% of late-stage cancers. EcDNAs drive tumor formation, evolution, and drug resistance by dynamically modulating oncogene copy-number and rewiring gene-regulatory networks. Elucidating the genomic architecture of ecDNA amplifications is critical for understanding tumor pathology and developing more effective therapies. Paired-end short-read (Illumina) sequencing and mapping have been utilized to represent ecDNA amplifications using a breakpoint graph, where the inferred architecture of ecDNA is encoded as a cycle in the graph. Traversals of breakpoint graph have been used to successfully predict ecDNA presence in cancer samples. However, short-read technologies are intrinsically limited in the identification of breakpoints, phasing together of complex rearrangements and internal duplications, and deconvolution of cell-to-cell heterogeneity of ecDNA structures. Long-read technologies, such as from Oxford Nanopore Technologies, have the potential to improve inference as the longer reads are better at mapping structural variants and are more likely to span rearranged or duplicated regions. Here, we propose CoRAL (Complete Reconstruction of Amplifications with Long reads), for reconstructing ecDNA architectures using long-read data. CoRAL reconstructs likely cyclic architectures using quadratic programming that simultaneously optimizes parsimony of reconstruction, explained copy number, and consistency of long-read mapping. CoRAL substantially improves reconstructions in extensive simulations and 9 datasets from previously-characterized cell-lines as compared to previous short-read-based tools. As long-read usage becomes wide-spread, we anticipate that CoRAL will be a valuable tool for profiling the landscape and evolution of focal amplifications in tumors.

Repeat-Unit Elongations To Produce Bacterial Complex Long Polysaccharide Chains, an O-Antigen Perspective

The O-antigen, a long polysaccharide that constitutes the distal part of the outer membrane-anchored lipopolysaccharide, is one of the critical components in the protective outer membrane of Gram-negative bacteria. Most species produce one of the structurally diverse O-antigens, with nearly all the polysaccharide components having complex structures made by the Wzx/Wzy pathway. This pathway produces repeat-units of mostly 3-8 sugars on the cytosolic face of the cytoplasmic membrane that is translocated by Wzx flippase to the periplasmic face and polymerized by Wzy polymerase to give long-chain polysaccharides. The Wzy polymerase is a highly diverse integral membrane protein typically containing 10-14 transmembrane segments. Biochemical evidence confirmed that Wzy polymerase is the sole driver of polymerization, and recent progress also began to demystify its interacting partner, Wzz, shedding some light to speculate how the proteins may operate together during polysaccharide biogenesis. However, our knowledge of how the highly variable Wzy proteins work as part of the O-antigen processing machinery remains poor. Here, we discuss the progress to the current understanding of repeat-unit polymerization and propose an updated model to explain the formation of additional short chain O-antigen polymers found in the lipopolysaccharide of diverse Gram-negative species and their importance in the biosynthetic process.

Pervasive correlations between causal disease effects of proximal SNPs vary with functional annotations and implicate stabilizing selection

The genetic architecture of human diseases and complex traits has been extensively studied, but little is known about the relationship of causal disease effect sizes between proximal SNPs, which have largely been assumed to be independent. We introduce a new method, LD SNP-pair effect correlation regression (LDSPEC), to estimate the correlation of causal disease effect sizes of derived alleles between proximal SNPs, depending on their allele frequencies, LD, and functional annotations; LDSPEC produced robust estimates in simulations across various genetic architectures. We applied LDSPEC to 70 diseases and complex traits from the UK Biobank (average N=306K), meta-analyzing results across diseases/traits. We detected significantly nonzero effect correlations for proximal SNP pairs (e.g., -0.37±0.09 for low-frequency positive-LD 0-100bp SNP pairs) that decayed with distance (e.g., -0.07±0.01 for low-frequency positive-LD 1-10kb), varied with allele frequency (e.g., -0.15±0.04 for common positive-LD 0-100bp), and varied with LD between SNPs (e.g., +0.12±0.05 for common negative-LD 0-100bp) (because we consider derived alleles, positive-LD and negative-LD SNP pairs may yield very different results). We further determined that SNP pairs with shared functions had stronger effect correlations that spanned longer genomic distances, e.g., -0.37±0.08 for low-frequency positive-LD same-gene promoter SNP pairs (average genomic distance of 47kb (due to alternative splicing)) and -0.32±0.04 for low-frequency positive-LD H3K27ac 0-1kb SNP pairs. Consequently, SNP-heritability estimates were substantially smaller than estimates of the sum of causal effect size variances across all SNPs (ratio of 0.87±0.02 across diseases/traits), particularly for certain functional annotations (e.g., 0.78±0.01 for common Super enhancer SNPs)-even though these quantities are widely assumed to be equal. We recapitulated our findings via forward simulations with an evolutionary model involving stabilizing selection, implicating the action of linkage masking, whereby haplotypes containing linked SNPs with opposite effects on disease have reduced effects on fitness and escape negative selection.

Promotion effects and mechanisms of molybdenum disulfide on the propagation of antibiotic resistance genes in soil

The rapid development of nanotechnology has aroused considerable attentions toward understanding the effects of engineered nanomaterials (ENMs) on the propagation of antibiotic resistance. Molybdenum disulfide (MoS₂) is an extensively used ENM and poses potential risks associated with environmental exposure; nevertheless, the role of MoS₂ toward antibiotic resistance genes (ARGs) transfer remains largely unknown. Herein, it was discovered that MoS₂ nanosheets accelerated the horizontal transfer of RP4 plasmid across Escherichia coli in a dose-dependent manner (0.5-10 mg/L), with the maximum transfer frequency 2.07-fold higher than that of the control. Integration of physiological, transcriptomics, and metabolomics analyses demonstrated that SOS response in bacteria was activated by MoS₂ due to the elevation of oxidative damage, accompanied by cell membrane permeabilization. MoS₂ promoted bacterial adhesion and intercellular contact via stimulating the secretion of extracellular polysaccharides. The ATP levels were maximally increased by 305.7 % upon exposure to MoS₂, and the expression of plasmid transfer genes was up-regulated, contributing to the accelerated plasmid conjugation and increased ARG abundance in soil. Our findings highlight the roles of emerging ENMs (e.g., MoS₂) in ARGs dissemination, which is significant for the safe applications and risk management of ENMs under the development scenarios of nanotechnology.

PNMA2 forms non-enveloped virus-like capsids that trigger paraneoplastic neurological syndrome

The paraneoplastic Ma antigen (PNMA) genes are associated with cancer-induced paraneoplastic syndromes that present with neurological symptoms and autoantibody production. How PNMA proteins trigger a severe autoimmune disease is unclear. PNMA genes are predominately expressed in the central nervous system with little known functions but are ectopically expressed in some tumors. Here, we show that PNMA2 is derived from a Ty3 retrotransposon that encodes a protein which forms virus-like capsids released from cells as non-enveloped particles. Recombinant PNMA2 capsids injected into mice induce a robust autoimmune reaction with significant generation of autoantibodies that preferentially bind external "spike" PNMA2 capsid epitopes, while capsid-assembly-defective PNMA2 protein is not immunogenic. PNMA2 autoantibodies present in cerebrospinal fluid of patients with anti-Ma2 paraneoplastic neurologic disease show similar preferential binding to PNMA2 "spike" capsid epitopes. These observations suggest that PNMA2 capsids released from tumors trigger an autoimmune response that underlies Ma2 paraneoplastic neurological syndrome.

Phosphatidylinositol-4-phosphate signaling regulates dense granule biogenesis and exocytosis in Toxoplasma gondii

Phosphoinositide metabolism defines the foundation of a major signaling pathway that is conserved throughout the eukaryotic kingdom. The 4-OH phosphorylated phosphoinositides such as phosphatidylinositol-4-phosphate (PtdIns4P) and phosphatidylinositol-4,5-bisphosphate are particularly important molecules as these execute intrinsically essential activities required for the viability of all eukaryotic cells studied thus far. Using intracellular tachyzoites of the apicomplexan parasite Toxoplasma gondii as model for assessing primordial roles for PtdIns4P signaling, we demonstrate the presence of PtdIns4P pools in Golgi/trans-Golgi (TGN) system and in post-TGN compartments of the parasite. Moreover, we show that deficits in PtdIns4P signaling result in structural perturbation of compartments that house dense granule cargo with accompanying deficits in dense granule exocytosis. Taken together, the data report a direct role for PtdIns4P in dense granule biogenesis and exocytosis. The data further indicate that the biogenic pathway for secretion-competent dense granule formation in T. gondii is more complex than simple budding of fully matured dense granules from the TGN.

Prokaryotic Genome Annotation

In the last decade, the high-throughput and relatively low cost of short-read sequencing technologies have revolutionized prokaryotic genomics. This has led to an exponential increase in the number of bacterial and archaeal genome sequences available, as well as corresponding increase of genome assembly and annotation tools developed. Together, these hardware and software technologies have given scientists unprecedented options to study their chosen microbial systems without the need for large teams of bioinformaticists or supercomputing facilities. While these analysis tools largely fall into only a few categories, each may have different requirements, caveats and file formats, and some may be rarely updated or even abandoned. And so, despite the apparent ease in sequencing and analyzing a prokaryotic genome, it is no wonder that the budding genomicist may quickly find oneself overwhelmed. Here, we aim to provide the reader with an overview of genome annotation and its most important considerations, as well as an easy-to-follow protocol to get started with annotating a prokaryotic genome.

The GASA Gene Family in Theobroma cacao: Genome wide Identification and Expression Analysis.. [DOI: 10.1101/2021.01.27.425041]

The gibberellic acid-stimulated Arabidopsis (GASA/GAST) gene family is widely distributed in plants. The role of the GASA gene family has been reported previously in various physiological and biological processes, such as cell division, root and seed development, stem growth, and fruit ripening. These genes also provide resistance to abiotic and biotic stresses including antimicrobial, antiviral, and antifungal. Here, we report 17 tcGASA genes in Theobroma cacao L. distributed on six chromosomes. The gene structure, promoter-region sequences, protein structure, and biochemical properties, expression, and phylogenetics of all tcGASAs were analyzed. Phylogenetic analyses divided tcGASA proteins into five groups. The nine segmentally duplicating genes form four pairs and cluster together in phylogenetic tree. Purifying selection pressure was recorded on tcGASA, including duplicated genes. Several stress/hormone-responsive cis-regulatory elements were also recognized in the promoter region of tcGASAs. Differential expression analyses revealed that most of the tcGASA genes showed elevated expression in the seeds (cacao food), implying their role in seed development. The black rod disease of genus Phytophthora caused up to 20–25% loss (700,000 metric tons) in world cacao production. The role of tcGASA genes in conferring fungal resistance was also explored based on RNAseq data against Phytophthora megakarya. The differential expression of tcGASA genes was recorded between the tolerant and susceptible cultivars of cacao plants, which were inoculated with the fungus for 24h and 72h. This differential expression indicating possible role of tcGASA genes to fungal resistant in cacao. Our findings provide new insight into the function, evolution, and regulatory system of the GASA family genes in T. cacao and provide new target genes for development of fungi-resistant cacao varieties in breeding programs.

CeO2 Nanoparticles Regulate the Propagation of Antibiotic Resistance Genes by Altering Cellular Contact and Plasmid Transfer

The dissemination and propagation of antibiotic resistance genes (ARGs) via plasmid-mediated conjugation pose a major threat to global public health. The potential effects of nanomaterials on ARGs fates have drawn much attention recently. In this study, CeO₂ nanoparticles (NPs), one of the typical nanomaterials proposed for increasing crop production, were applied at the concentration range of 1-50 mg/L to investigate their effects on ARGs transfer between Escherichia coli. Our results revealed that the conjugative transfer of RP4 plasmid was enhanced by 118-123% at relatively high concentrations (25 and 50 mg/L) of CeO₂ NPs, however, CeO₂ NPs at low concentrations (1 and 5 mg/L) inhibited the transfer by 22-26%. The opposite effect at low concentrations is mainly attributed to (i) the reduced ROS level, (ii) the weakened intercellular contact via inhibiting the synthesis of polysaccharides in extracellular polymeric substances, and (iii) the down-regulated expression of plasmid transfer genes due to the shortage of ATP supply. Our findings highlight the distinct dose-dependent responses of ARGs conjugative transfer, providing evidence for selecting appropriate NPs dose to reduce the spread of ARGs while applying nanoagrotechnology.

Peptide-based quorum sensing systems in Paenibacillus polymyxa

Discovery of conserved communication systems in the agriculturally important Paenibacillus bacteria. These systems are widespread, and some species encode more than 25 different peptide-receptor pairs.

Paenibacillus polymyxa is an agriculturally important plant growth–promoting rhizobacterium. Many Paenibacillus species are known to be engaged in complex bacteria–bacteria and bacteria–host interactions, which in other species were shown to necessitate quorum sensing communication. However, to date, no quorum sensing systems have been described in Paenibacillus. Here, we show that the type strain P. polymyxa ATCC 842 encodes at least 16 peptide-based communication systems. Each of these systems is comprised of a pro-peptide that is secreted to the growth medium and processed to generate a mature short peptide. Each peptide has a cognate intracellular receptor of the RRNPP family, and we show that external addition of P. polymyxa communication peptides leads to reprogramming of the transcriptional response. We found that these quorum sensing systems are conserved across hundreds of species belonging to the Paenibacillaceae family, with some species encoding more than 25 different peptide-receptor pairs, representing a record number of quorum sensing systems encoded in a single genome.

Evolutionary dynamics of natural product biosynthesis in bacteria

Covering: 2008 up to 2019The forces of biochemical adaptive evolution operate at the level of genes, manifesting in complex phenotypes and the global biodiversity of proteins and metabolites. While evolutionary histories have been deciphered for some other complex traits, the origins of natural product biosynthesis largely remain a mystery. This fundamental knowledge gap is surprising given the many decades of research probing the genetic, chemical, and biophysical mechanisms of bacterial natural product biosynthesis. Recently, evolutionary thinking has begun to permeate this otherwise mechanistically dominated field. Natural products are now sometimes referred to as 'specialized' rather than 'secondary' metabolites, reinforcing the importance of their biological and ecological functions. Here, we review known evolutionary mechanisms underlying the overwhelming chemical diversity of bacterial secondary metabolism, focusing on enzyme promiscuity and the evolution of enzymatic domains that enable metabolic traits. We discuss the mechanisms that drive the assembly of natural product biosynthetic gene clusters and propose formal definitions for 'specialized' and 'secondary' metabolism. We further explore how biosynthetic gene clusters evolve to synthesize related molecular species, and in turn how the biological and ecological roles that emerge from metabolic diversity are acted on by selection. Finally, we reconcile chemical, functional, and genetic data into an evolutionary model, the dynamic chemical matrix evolutionary hypothesis, in which the relationships between chemical distance, biomolecular activity, and relative fitness shape adaptive landscapes.

In silico characterization of hypothetical proteins from Orientia tsutsugamushi str. Karp uncovers virulence genes

Scrub typhus also known as bush typhus is a disease with symptoms similar to Chikungunya infection. It is caused by a gram-negative bacterium Orientia tsutsugamushi which resides in its vertebrate host, Mites. The genome of Orientia tsutsugamushi str. Karp encodes for 1,563 proteins, of which 344 are characterized as hypothetical ones. In the present study, we tried to identify the probable functions of these 344 hypothetical proteins (HPs). All the characterized hypothetical proteins (HPs) belong to the various protein classes like enzymes, transporters, binding proteins, metabolic process and catalytic activity and kinase activity. These hypothetical proteins (HPs) were further analyzed for virulence factors with 62 proteins identified as the most virulent proteins among these hypothetical proteins (HPs). In addition, we studied the protein sequence similarity network for visualizing functional trends across protein superfamilies from the context of sequence similarity and it shows great potential for generating testable hypotheses about protein structure-function relationships. Furthermore, we calculated toplogical properties of the network and found them to obey network power law distributions showing a fractal nature. We also identifed two highly interconnected modules in the main network which contained five hub proteins (KJV55465, KJV56211, KJV57212, KJV57203 and KJV57216) having 1.0 clustering coefficient. The structural modeling (2D and 3D structure) of these five hub proteins was carried out and the catalytic site essential for its functioning was analyzed. The outcome of the present study may facilitate a better understanding of the mechanism of virulence, pathogenesis, adaptability to host and up-to-date annotations will make unknown genes easy to identify and target for experimentation. The information on the functional attributes and virulence characteristic of these hypothetical proteins (HPs) are envisaged to facilitate effective development of novel antibacterial drug targets of Orientia tsutsugamushi.

Harnessing glycoenzyme engineering for synthesis of bioactive oligosaccharides

Combined with chemical synthesis, the use of glycoenzyme biocatalysts has shown great synthetic potential over recent decades owing to their remarkable versatility in terms of substrates and regio- and stereoselectivity that allow structurally controlled synthesis of carbohydrates and glycoconjugates. Nonetheless, the lack of appropriate enzymatic tools with requisite properties in the natural diversity has hampered extensive exploration of enzyme-based synthetic routes to access relevant bioactive oligosaccharides, such as cell-surface glycans or prebiotics. With the remarkable progress in enzyme engineering, it has become possible to improve catalytic efficiency and physico-chemical properties of enzymes but also considerably extend the repertoire of accessible catalytic reactions and tailor novel substrate specificities. In this review, we intend to give a brief overview of the advantageous use of engineered glycoenzymes, sometimes in combination with chemical steps, for the synthesis of natural bioactive oligosaccharides or their precursors. The focus will be on examples resulting from the three main classes of glycoenzymes specialized in carbohydrate synthesis: glycosyltransferases, glycoside hydrolases and glycoside phosphorylases.

NOVOPlasty: de novo assembly of organelle genomes from whole genome data

The evolution in next-generation sequencing (NGS) technology has led to the development of many different assembly algorithms, but few of them focus on assembling the organelle genomes. These genomes are used in phylogenetic studies, food identification and are the most deposited eukaryotic genomes in GenBank. Producing organelle genome assembly from whole genome sequencing (WGS) data would be the most accurate and least laborious approach, but a tool specifically designed for this task is lacking. We developed a seed-and-extend algorithm that assembles organelle genomes from whole genome sequencing (WGS) data, starting from a related or distant single seed sequence. The algorithm has been tested on several new (Gonioctena intermedia and Avicennia marina) and public (Arabidopsis thaliana and Oryza sativa) whole genome Illumina data sets where it outperforms known assemblers in assembly accuracy and coverage. In our benchmark, NOVOPlasty assembled all tested circular genomes in less than 30 min with a maximum memory requirement of 16 GB and an accuracy over 99.99%. In conclusion, NOVOPlasty is the sole de novo assembler that provides a fast and straightforward extraction of the extranuclear genomes from WGS data in one circular high quality contig. The software is open source and can be downloaded at https://github.com/ndierckx/NOVOPlasty.

Structure-activity relationships in a new class of non-substrate-like covalent inhibitors of the bacterial glycosyltransferase LgtC

Lipooligosaccharide (LOS) structures in the outer core of Gram-negative mucosal pathogens such as Neisseria meningitidis and Haemophilus influenzae contain characteristic glycoepitopes that contribute significantly to bacterial virulence. An important example is the digalactoside epitope generated by the retaining α-1,4-galactosyltransferase LgtC. These digalactosides camouflage the pathogen from the host immune system and increase its serum resistance. Small molecular inhibitors of LgtC are therefore sought after as chemical tools to study bacterial virulence, and as potential candidates for anti-virulence drug discovery. We have recently discovered a new class of non-substrate-like inhibitors of LgtC. The new inhibitors act via a covalent mode of action, targeting a non-catalytic cysteine residue in the LgtC active site. Here, we describe, for the first time, structure-activity relationships for this new class of glycosyltransferase inhibitors. We have carried out a detailed analysis of the inhibition kinetics to establish the relative contribution of the non-covalent binding and the covalent inactivation steps for overall inhibitory activity. Selected inhibitors were also evaluated against a serum-resistant strain of Haemophilus influenzae, but did not enhance the killing effect of human serum.

Identification and verification of potential piRNAs from domesticated yak testis

PIWI-interacting RNAs (piRNA) are small non-coding RNA molecules expressed in animal germ cells that interact with PIWI family proteins to form RNA–protein complexes involved in epigenetic and post-transcriptional gene silencing of retrotransposons and other genetic elements in germ line cells, including reproductive stem cell self-sustainment, differentiation, meiosis and spermatogenesis. In the present study, we performed high-throughput sequencing of piRNAs in testis samples from yaks in different stages of sexual maturity. Deep sequencing of the small RNAs (18–40 nt in length) yielded 4,900,538 unique reads from a total of 53,035,635 reads. We identified yak small RNAs (18–30 nt) and performed functional characterization. Yak small RNAs showed a bimodal length distribution, with two peaks at 22 nt and >28 nt. More than 80% of the 3,106,033 putative piRNAs were mapped to 4637 piRNA-producing genomic clusters using RPKM. 6388 candidate piRNAs were identified from clean reads and the annotations were compared with the yak reference genome repeat region. Integrated network analysis suggested that some differentially expressed genes were involved in spermatogenesis through ECM–receptor interaction and PI3K-Akt signaling pathways. Our data provide novel insights into the molecular expression and regulation similarities and diversities in spermatogenesis and testicular development in yaks at different stages of sexual maturity.

YvcK, a protein required for cell wall integrity and optimal carbon source utilization, binds uridine diphosphate-sugars

In Bacillus subtilis, Listeria monocytogenes and in two Mycobacteria, it was previously shown that yvcK is a gene required for normal cell shape, for optimal carbon source utilization and for virulence of pathogenic bacteria. Here we report that the B. subtilis protein YvcK binds to Uridine diphosphate-sugars like Uridine diphosphate-Glucose (UDP-Glc) and Uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) in vitro. Using the crystal structure of Bacillus halodurans YvcK, we identified residues involved in this interaction. We tested the effect of point mutations affecting the ability of YvcK to bind UDP-sugars on B. subtilis physiology and on cell size. Indeed, it was shown that UDP-Glc serves as a metabolic signal to regulate B. subtilis cell size. Interestingly, we observed that, whereas a yvcK deletion results in the formation of unusually large cells, inactivation of YvcK UDP-sugar binding site does not affect cell length. However, these point mutations result in an increased sensitivity to bacitracin, an antibiotic which targets peptidoglycan synthesis. We thus propose that UDP-GlcNAc, a precursor of peptidoglycan, could be a good physiological ligand candidate of YvcK.

FEELnc: a tool for long non-coding RNA annotation and its application to the dog transcriptome

Whole transcriptome sequencing (RNA-seq) has become a standard for cataloguing and monitoring RNA populations. One of the main bottlenecks, however, is to correctly identify the different classes of RNAs among the plethora of reconstructed transcripts, particularly those that will be translated (mRNAs) from the class of long non-coding RNAs (lncRNAs). Here, we present FEELnc (FlExible Extraction of LncRNAs), an alignment-free program that accurately annotates lncRNAs based on a Random Forest model trained with general features such as multi k-mer frequencies and relaxed open reading frames. Benchmarking versus five state-of-the-art tools shows that FEELnc achieves similar or better classification performance on GENCODE and NONCODE data sets. The program also provides specific modules that enable the user to fine-tune classification accuracy, to formalize the annotation of lncRNA classes and to identify lncRNAs even in the absence of a training set of non-coding RNAs. We used FEELnc on a real data set comprising 20 canine RNA-seq samples produced by the European LUPA consortium to substantially expand the canine genome annotation to include 10 374 novel lncRNAs and 58 640 mRNA transcripts. FEELnc moves beyond conventional coding potential classifiers by providing a standardized and complete solution for annotating lncRNAs and is freely available at https://github.com/tderrien/FEELnc.

Auxin-induced expression divergence between Arabidopsis species may originate within the TIR1/AFB-AUX/IAA-ARF module

Auxin is an essential regulator of plant growth and development, and auxin signaling components are conserved among land plants. Yet, a remarkable degree of natural variation in physiological and transcriptional auxin responses has been described among Arabidopsis thaliana accessions. As intraspecies comparisons offer only limited genetic variation, we here inspect the variation of auxin responses between A. thaliana and A. lyrata. This approach allowed the identification of conserved auxin response genes including novel genes with potential relevance for auxin biology. Furthermore, promoter divergences were analyzed for putative sources of variation. De novo motif discovery identified novel and variants of known elements with potential relevance for auxin responses, emphasizing the complex, and yet elusive, code of element combinations accounting for the diversity in transcriptional auxin responses. Furthermore, network analysis revealed correlations of interspecies differences in the expression of AUX/IAA gene clusters and classic auxin-related genes. We conclude that variation in general transcriptional and physiological auxin responses may originate substantially from functional or transcriptional variations in the TIR1/AFB, AUX/IAA, and ARF signaling network. In that respect, AUX/IAA gene expression divergence potentially reflects differences in the manner in which different species transduce identical auxin signals into gene expression responses.

Upgrading short-read animal genome assemblies to chromosome level using comparative genomics and a universal probe set

Most recent initiatives to sequence and assemble new species’ genomes de novo fail to achieve the ultimate endpoint to produce contigs, each representing one whole chromosome. Even the best-assembled genomes (using contemporary technologies) consist of subchromosomal-sized scaffolds. To circumvent this problem, we developed a novel approach that combines computational algorithms to merge scaffolds into chromosomal fragments, PCR-based scaffold verification, and physical mapping to chromosomes. Multigenome-alignment-guided probe selection led to the development of a set of universal avian BAC clones that permit rapid anchoring of multiple scaffolds to chromosomes on all avian genomes. As proof of principle, we assembled genomes of the pigeon (Columbia livia) and peregrine falcon (Falco peregrinus) to chromosome levels comparable, in continuity, to avian reference genomes. Both species are of interest for breeding, cultural, food, and/or environmental reasons. Pigeon has a typical avian karyotype (2n = 80), while falcon (2n = 50) is highly rearranged compared to the avian ancestor. By using chromosome breakpoint data, we established that avian interchromosomal breakpoints appear in the regions of low density of conserved noncoding elements (CNEs) and that the chromosomal fission sites are further limited to long CNE “deserts.” This corresponds with fission being the rarest type of rearrangement in avian genome evolution. High-throughput multiple hybridization and rapid capture strategies using the current BAC set provide the basis for assembling numerous avian (and possibly other reptilian) species, while the overall strategy for scaffold assembly and mapping provides the basis for an approach that (provided metaphases can be generated) could be applied to any animal genome.

Understanding Biological Roles of Venoms Among the Caenophidia: The Importance of Rear-Fanged Snakes

Snake venoms represent an adaptive trophic response to the challenges confronting a limbless predator for overcoming combative prey, and this chemical means of subduing prey shows several dominant phenotypes. Many front-fanged snakes, particularly vipers, feed on various vertebrate and invertebrate prey species, and some of their venom components (e.g., metalloproteinases, cobratoxin) appear to have been selected for "broad-brush" incapacitation of different prey taxa. Using proteomic and genomic techniques, the compositional diversity of front-fanged snakes is becoming well characterized; however, this is not the case for most rear-fanged colubroid snakes. Because these species consume a high diversity of prey, and because venoms are primarily a trophic adaptation, important clues for understanding specific selective pressures favoring venom component composition will be found among rear-fanged snake venoms. Rear-fanged snakes typically (but not always) produce venoms with lower complexity than front-fanged snakes, and there are even fewer dominant (and, arguably, biologically most relevant) venom protein families. We have demonstrated taxon-specific toxic effects, where lizards and birds show high susceptibility while mammals are largely unaffected, for both Old World and New World rear-fanged snakes, strongly indicating a causal link between toxin evolution and prey preference. New data are presented on myotoxin a, showing that the extremely rapid paralysis induced by this rattlesnake toxin is specific for rodents, and that myotoxin a is ineffectual against lizards. Relatively few rear-fanged snake venoms have been characterized, and basic natural history data are largely lacking, but directed sampling of specialized species indicates that novel compounds are likely among these specialists, particularly among those species feeding on invertebrate prey such as scorpions and centipedes. Because many of the more than 2200 species of colubroid snakes are rear-fanged, and many possess a Duvernoy's venom gland, understanding the nature of their venoms is foundational to understanding venom evolution in advanced snakes.

Maps of context-dependent putative regulatory regions and genomic signal interactions

Gene transcription is regulated mainly by transcription factors (TFs). ENCODE and Roadmap Epigenomics provide global binding profiles of TFs, which can be used to identify regulatory regions. To this end we implemented a method to systematically construct cell-type and species-specific maps of regulatory regions and TF-TF interactions. We illustrated the approach by developing maps for five human cell-lines and two other species. We detected ∼144k putative regulatory regions among the human cell-lines, with the majority of them being ∼300 bp. We found ∼20k putative regulatory elements in the ENCODE heterochromatic domains suggesting a large regulatory potential in the regions presumed transcriptionally silent. Among the most significant TF interactions identified in the heterochromatic regions were CTCF and the cohesin complex, which is in agreement with previous reports. Finally, we investigated the enrichment of the obtained putative regulatory regions in the 3D chromatin domains. More than 90% of the regions were discovered in the 3D contacting domains. We found a significant enrichment of GWAS SNPs in the putative regulatory regions. These significant enrichments provide evidence that the regulatory regions play a crucial role in the genomic structural stability. Additionally, we generated maps of putative regulatory regions for prostate and colorectal cancer human cell-lines.

Stress-induced transposon reactivation: a mediator or an estimator of allostatic load?

Transposons are playing an important role in the evolution of eukaryotic genomes. These endogenous virus-like elements often amplify within their host genomes in a species specific manner. Today we have limited understanding when and how these amplification events happens. What we do know is that cells have evolved multiple line of defenses to keep these potentially invasive elements under control, often involving epigenetic mechanisms such as DNA-methylation and histone modifications. Emerging evidence shows a strong link between transposon activity and human aging and diseases, as well as a role for transposons in normal brain development. Controlling transposon activity may therefore uphold the fine balance between health and disease. In this article we investigate this balance, and sets it in relation to allostatic load, which conceptualize the link between stress and the "wear and tear" of the organism that leads to aging and disease. We hypothesize that stress-induced retrotransposon reactivation in humans may be used to estimate allostatic load, and may be a possible mechanism in which transposons amplify within species genomes.

Systematic Exploration of the Glycoproteome of the Beneficial Gut Isolate Lactobacillus rhamnosus GG

Glycoproteins form an interesting class of macromolecules involved in bacterial-host interactions, but they are not yet widely explored in Gram-positive and beneficial species. Here, an integrated and widely applicable approach was followed to identify putative bacterial glycoproteins, combining proteome fractionation with 2D protein and glycostained gels and lectin blots. This approach was validated for the microbiota isolate Lactobacillus rhamnosus GG. The approach resulted in a list of putative glycosylated proteins receiving a 'glycosylation score'. Ultimately, we could identify 41 unique glycosylated proteins in L. rhamnosus GG (6 top-confidence, 10 high-confidence and 25 putative hits; classification based on glycosylation score). Most glycoproteins are associated with the cell wall and membrane. Identified glycoproteins include proteins involved in transport, translation, and sugar metabolism processes. A robust screening resulted in a comprehensive mapping of glycoproteins in L. rhamnosus GG. Our results reflect the glycosylation of sugar metabolism enzymes, transporters, and other proteins crucial for cell physiology. We hypothesize that protein glycosylation can confer an extra level of regulation, for example by affecting enzyme functions. This is the first systematic study of the glycoproteome of a probiotic and beneficial gut isolate.

Plant secondary metabolism linked glycosyltransferases: An update on expanding knowledge and scopes

The multigene family of enzymes known as glycosyltransferases or popularly known as GTs catalyze the addition of carbohydrate moiety to a variety of synthetic as well as natural compounds. Glycosylation of plant secondary metabolites is an emerging area of research in drug designing and development. The unsurpassing complexity and diversity among natural products arising due to glycosylation type of alterations including glycodiversification and glycorandomization are emerging as the promising approaches in pharmacological studies. While, some GTs with broad spectrum of substrate specificity are promising candidates for glycoengineering while others with stringent specificity pose limitations in accepting molecules and performing catalysis. With the rising trends in diseases and the efficacy/potential of natural products in their treatment, glycosylation of plant secondary metabolites constitutes a key mechanism in biogeneration of their glycoconjugates possessing medicinal properties. The present review highlights the role of glycosyltransferases in plant secondary metabolism with an overview of their identification strategies, catalytic mechanism and structural studies on plant GTs. Furthermore, the article discusses the biotechnological and biomedical application of GTs ranging from detoxification of xenobiotics and hormone homeostasis to the synthesis of glycoconjugates and crop engineering. The future directions in glycosyltransferase research should focus on the synthesis of bioactive glycoconjugates via metabolic engineering and manipulation of enzyme's active site leading to improved/desirable catalytic properties. The multiple advantages of glycosylation in plant secondary metabolomics highlight the increasing significance of the GTs, and in near future, the enzyme superfamily may serve as promising path for progress in expanding drug targets for pharmacophore discovery and development.

EXPLoRA-web: linkage analysis of quantitative trait loci using bulk segregant analysis

Identification of genomic regions associated with a phenotype of interest is a fundamental step toward solving questions in biology and improving industrial research. Bulk segregant analysis (BSA) combined with high-throughput sequencing is a technique to efficiently identify these genomic regions associated with a trait of interest. However, distinguishing true from spuriously linked genomic regions and accurately delineating the genomic positions of these truly linked regions requires the use of complex statistical models currently implemented in software tools that are generally difficult to operate for non-expert users. To facilitate the exploration and analysis of data generated by bulked segregant analysis, we present EXPLoRA-web, a web service wrapped around our previously published algorithm EXPLoRA, which exploits linkage disequilibrium to increase the power and accuracy of quantitative trait loci identification in BSA analysis. EXPLoRA-web provides a user friendly interface that enables easy data upload and parallel processing of different parameter configurations. Results are provided graphically and as BED file and/or text file and the input is expected in widely used formats, enabling straightforward BSA data analysis. The web server is available at http://bioinformatics.intec.ugent.be/explora-web/.

Plant basal resistance to nematodes: an update

Most plant-parasitic nematodes are obligate biotrophs feeding on the roots of their hosts. Whereas ectoparasites remain on the root surface and feed on the outer cell layers, endoparasitic nematodes enter the host to parasitize cells around or within the central cylinder. Nematode invasion and feeding causes tissue damage which may, in turn, lead to the activation of host basal defence responses. Hitherto, research interests in plant-nematode interaction have emphasized effector-triggered immunity rather than basal plant defence responses. However, some recent investigations suggest that basal defence pathways are not only activated but also play an important role in determining interaction outcomes. In this review we discuss the major findings and point out future directions to dissect the molecular mechanisms underlying plant basal defence to nematodes further.

Bacterial Glycosyltransferases: Challenges and Opportunities of a Highly Diverse Enzyme Class Toward Tailoring Natural Products

The enzyme subclass of glycosyltransferases (GTs; EC 2.4) currently comprises 97 families as specified by CAZy classification. One of their important roles is in the biosynthesis of disaccharides, oligosaccharides, and polysaccharides by catalyzing the transfer of sugar moieties from activated donor molecules to other sugar molecules. In addition GTs also catalyze the transfer of sugar moieties onto aglycons, which is of great relevance for the synthesis of many high value natural products. Bacterial GTs show a higher sequence similarity in comparison to mammalian ones. Even when most GTs are poorly explored, state of the art technologies, such as protein engineering, domain swapping or computational analysis strongly enhance our understanding and utilization of these very promising classes of proteins. This perspective article will focus on bacterial GTs, especially on classification, screening and engineering strategies to alter substrate specificity. The future development in these fields as well as obstacles and challenges will be highlighted and discussed.

Essential Amino Acid Supplementation by Gut Microbes of a Wood-Feeding Cerambycid

Insects are unable to synthesize essential amino acids (EAAs) de novo, thus rely on dietary or symbiotic sources for them. Wood is a poor resource of nitrogen in general, and EAAs in particular. In this study, we investigated whether gut microbiota of the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), a cerambycid that feeds in the heartwood of healthy host trees, serve as sources of EAAs to their host under different dietary conditions. δ(13)C-stable isotope analyses revealed significant δ(13)C-enrichment (3.4 ± 0.1‰; mean ± SEM) across five EAAs in wood-fed larvae relative to their woody diet. δ(13)C values for the consumers greater than 1‰ indicate significant contributions from non-dietary EAA sources (symbionts in this case). In contrast, δ(13)C-enrichment of artificial diet-fed larvae (controls) relative to their food source was markedly less (1.7 ± 0.1‰) than was observed in wood-fed larvae, yet still exceeded the threshold of 1‰. A predictive model based on δ(13)CEAA signatures of five EAAs from representative bacterial, fungal, and plant samples identified symbiotic bacteria and fungi as the likely supplementary sources of EAA in wood-fed larvae. Using the same model, but with an artificial diet as the dietary source, we identified minor supplementary bacterial sources of EAA in artificial diet-fed larvae. This study highlights how microbes associated with A. glabripennis can serve as a source of EAAs when fed on nutrient-limited diets, potentially circumventing the dietary limitations of feeding on woody substrates.

Response of yeast cells to high glucose involves molecular and physiological differences when compared to other osmostress conditions

Yeast cells can be affected by several causes of osmotic stress, such as high salt, sorbitol or glucose concentrations. The last condition is particularly interesting during natural processes where this microorganism participates. Response to osmostress requires the HOG (High Osmolarity Glycerol) pathway and several transcription factors, including Hot1, which plays a key role in high glucose concentrations. In this work, we describe how the yeast response to osmotic stress shows differences in accordance with the stress agent responsible for it. Compared with other conditions, under high glucose stress, delocalization of MAPK (Mitogen-Activated Protein Kinase) Hog1 is slower, induction of HOT1 expression is higher and Msn2/4 transcription factors are involved to a lesser extent. The transcriptomic analyses carried out with samples incubated for 30 min in the presence of high glucose or sorbitol reveal the presence of two functional categories with a differential expression between these conditions: glycogen biosynthesis and mobilization, and membrane-anchored proteins. We present data to demonstrate that the cells treated with 20% (w/v) (1.11 M) glucose contain higher chitin levels and are more sensitive to calcofluor white and ethanol.

The sweet tooth of bacteria: common themes in bacterial glycoconjugates

Humans have been increasingly recognized as being superorganisms, living in close contact with a microbiota on all their mucosal surfaces. However, most studies on the human microbiota have focused on gaining comprehensive insights into the composition of the microbiota under different health conditions (e.g., enterotypes), while there is also a need for detailed knowledge of the different molecules that mediate interactions with the host. Glycoconjugates are an interesting class of molecules for detailed studies, as they form a strain-specific barcode on the surface of bacteria, mediating specific interactions with the host. Strikingly, most glycoconjugates are synthesized by similar biosynthesis mechanisms. Bacteria can produce their major glycoconjugates by using a sequential or an en bloc mechanism, with both mechanistic options coexisting in many species for different macromolecules. In this review, these common themes are conceptualized and illustrated for all major classes of known bacterial glycoconjugates, with a special focus on the rather recently emergent field of glycosylated proteins. We describe the biosynthesis and importance of glycoconjugates in both pathogenic and beneficial bacteria and in both Gram-positive and -negative organisms. The focus lies on microorganisms important for human physiology. In addition, the potential for a better knowledge of bacterial glycoconjugates in the emerging field of glycoengineering and other perspectives is discussed.

Towards a better understanding of Lactobacillus rhamnosus GG--host interactions

Lactobacillus rhamnosus GG (LGG) is one of the most widely used probiotic strains. Various health effects are well documented including the prevention and treatment of gastro-intestinal infections and diarrhea, and stimulation of immune responses that promote vaccination or even prevent certain allergic symptoms. However, not all intervention studies could show a clinical benefit and even for the same conditions, the results are not univocal. Clearly, the host phenotype governed by age, genetics and environmental factors such as the endogenous microbiota, plays a role in whether individuals are responders or non-responders. However, we believe that a detailed knowledge of the bacterial physiology and the LGG molecules that play a key role in its host-interaction capacity is crucial for a better understanding of its potential health benefits. Molecules that were yet identified as important factors governing host interactions include its adhesive pili or fimbriae, its lipoteichoic acid molecules, its major secreted proteins and its galactose-rich exopolysaccharides, as well as specific DNA motifs. Nevertheless, future studies are needed to correlate specific health effects to these molecular effectors in LGG, and also in other probiotic strains.