scholarly journals In-Frame Deletions Allow Functional Characterization of Complex Cellulose Degradation Phenotypes in Cellvibrio japonicus

2015 ◽  
Vol 81 (17) ◽  
pp. 5968-5975 ◽  
Author(s):  
Cassandra E. Nelson ◽  
Jeffrey G. Gardner
Keyword(s):  
Cellulose Degradation ◽  
Functional Characterization ◽  
Growth Conditions ◽  
Model Organisms ◽  
Lignocellulose Degradation ◽  
Single Mutation ◽  
Gene Deletions ◽  
Content Type ◽  
Degrading Bacterium ◽  
Cellvibrio Japonicus

ABSTRACTThe depolymerization of the recalcitrant polysaccharides found in lignocellulose has become an area of intense interest due to the role of this process in global carbon cycling, human gut microbiome nutritional contributions, and bioenergy production. However, underdeveloped genetic tools have hampered study of bacterial lignocellulose degradation, especially outside model organisms. In this report, we describe an in-frame deletion strategy for the Gram-negative lignocellulose-degrading bacteriumCellvibrio japonicus. This method leverages optimized growth conditions for conjugation andsacBcounterselection for the generation of markerless in-frame deletions. This method produces mutants in as few as 8 days and allows for the ability to make multiple gene deletions per strain. It is also possible to remove large sections of the genome, as shown in this report with the deletion of the nine-gene (9.4-kb)gspoperon inC. japonicus.We applied this system to study the complex phenotypes of cellulose degradation inC. japonicus. Our data indicated that a Δcel5BΔcel6Adouble mutant is crippled for cellulose utilization, more so than by either single mutation alone. Additionally, we deleted individual genes in the two-genecbp2EDoperon and showed that both genes contribute to cellulose degradation inC. japonicus. Overall, these described techniques substantially enhance the utility ofC. japonicusas a model system to study lignocellulose degradation.

scholarly journals Autophagy-Related Protein ATG8 Has a Noncanonical Function for Apicoplast Inheritance in Toxoplasma gondii

mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Maude F. Lévêque ◽  
Laurence Berry ◽  
Michael J. Cipriano ◽  
Hoa-Mai Nguyen ◽  
Boris Striepen ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Growth Conditions ◽  
Model Organisms ◽  
Secondary Endosymbiosis ◽  
Related Protein ◽  
Content Type ◽  
Superresolution Microscopy ◽  
Animal Pathogens ◽  
Cellular Components ◽  
Catabolic Process

ABSTRACT Autophagy is a catabolic process widely conserved among eukaryotes that permits the rapid degradation of unwanted proteins and organelles through the lysosomal pathway. This mechanism involves the formation of a double-membrane structure called the autophagosome that sequesters cellular components to be degraded. To orchestrate this process, yeasts and animals rely on a conserved set of autophagy-related proteins (ATGs). Key among these factors is ATG8, a cytoplasmic protein that is recruited to nascent autophagosomal membranes upon the induction of autophagy. Toxoplasma gondii is a potentially harmful human pathogen in which only a subset of ATGs appears to be present. Although this eukaryotic parasite seems able to generate autophagosomes upon stresses such as nutrient starvation, the full functionality and biological relevance of a canonical autophagy pathway are as yet unclear. Intriguingly, in T. gondii, ATG8 localizes to the apicoplast under normal intracellular growth conditions. The apicoplast is a nonphotosynthetic plastid enclosed by four membranes resulting from a secondary endosymbiosis. Using superresolution microscopy and biochemical techniques, we show that TgATG8 localizes to the outermost membrane of this organelle. We investigated the unusual function of TgATG8 at the apicoplast by generating a conditional knockdown mutant. Depletion of TgATG8 led to rapid loss of the organelle and subsequent intracellular replication defects, indicating that the protein is essential for maintaining apicoplast homeostasis and thus for survival of the tachyzoite stage. More precisely, loss of TgATG8 led to abnormal segregation of the apicoplast into the progeny because of a loss of physical interactions of the organelle with the centrosomes. IMPORTANCE By definition, autophagy is a catabolic process that leads to the digestion and recycling of eukaryotic cellular components. The molecular machinery of autophagy was identified mainly in model organisms such as yeasts but remains poorly characterized in phylogenetically distant apicomplexan parasites. We have uncovered an unusual function for autophagy-related protein ATG8 in Toxoplasma gondii: TgATG8 is crucial for normal replication of the parasite inside its host cell. Seemingly unrelated to the catabolic autophagy process, TgATG8 associates with the outer membrane of the nonphotosynthetic plastid harbored by the parasite called the apicoplast, and there it plays an important role in the centrosome-driven inheritance of the organelle during cell division. This not only reveals an unexpected function for an autophagy-related protein but also sheds new light on the division process of an organelle that is vital to a group of important human and animal pathogens.

scholarly journals Regulation of Bioluminescence in Photobacterium leiognathi Strain KNH6

2015 ◽  
Vol 197 (23) ◽  
pp. 3676-3685 ◽  
Author(s):  
Anne K. Dunn ◽  
Bethany A. Rader ◽  
Eric V. Stabb ◽  
Mark J. Mandel
Keyword(s):  
Tca Cycle ◽  
Growth Conditions ◽  
Model Organisms ◽  
Content Type ◽  
Dna And Rna ◽  
Apply Genetic ◽  
Light Production ◽  
Photobacterium Leiognathi ◽  
Pheromone Signaling ◽  
Luminous Bacteria

ABSTRACTBacterial bioluminescence is taxonomically restricted to certain proteobacteria, many of which belong to theVibrionaceae. In the most well-studied cases, pheromone signaling plays a key role in regulation of light production. However, previous reports have indicated that certainPhotobacteriumstrains do not use this regulatory method for controlling luminescence. In this study, we combined genome sequencing with genetic approaches to characterize the regulation of luminescence inPhotobacterium leiognathistrain KNH6, an extremely bright isolate. Using transposon mutagenesis and screening for decreased luminescence, we identified insertions in genes encoding components necessary for the luciferase reaction (lux,lum, andriboperons) as well as in nine other loci. These additional loci encode gene products predicted to be involved in the tricarboxylic acid (TCA) cycle, DNA and RNA metabolism, transcriptional regulation, and the synthesis of cytochromec, peptidoglycan, and fatty acids. The mutagenesis screen did not identify any mutants with disruptions of predicted pheromone-related loci. Using targeted gene insertional disruptions, we demonstrate that under the growth conditions tested, luminescence levels do not appear to be controlled through canonical pheromone signaling systems in this strain.IMPORTANCEDespite the long-standing interest in luminous bacteria, outside a few model organisms, little is known about the regulation and function of luminescence. Light-producing marine bacteria are widely distributed and have diverse lifestyles, suggesting that the control and significance of luminescence may be similarly diverse. In this study, we apply genetic tools to the study of regulation of light production in the extremely bright isolatePhotobacterium leiognathiKNH6. Our results suggest an unusual lack of canonical pheromone-mediated control of luminescence and contribute to a better understanding of alternative strategies for regulation of a key bacterial behavior. These experiments lay the groundwork for further study of the regulation and role of bioluminescence inP. leiognathi.

scholarly journals Barriers to 3-Hydroxypropionate-Dependent Growth of Rhodobacter sphaeroides by Distinct Disruptions of the Ethylmalonyl Coenzyme A Pathway

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Steven J. Carlson ◽  
Angela Fleig ◽  
M. Kelsey Baron ◽  
Ivan A. Berg ◽  
Birgit E. Alber
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Drug Target ◽  
Coenzyme A ◽  
Growth Conditions ◽  
Gene Encoding ◽  
Gene Deletions ◽  
Content Type ◽  
Growth Defects ◽  
Dependent Growth

ABSTRACT Rhodobacter sphaeroides is able to use 3-hydroxypropionate as the sole carbon source through the reductive conversion of 3-hydroxypropionate to propionyl coenzyme A (propionyl-CoA). The ethylmalonyl-CoA pathway is not required in this process because a crotonyl-CoA carboxylase/reductase (Ccr)-negative mutant still grew with 3-hydroxypropionate. Much to our surprise, a mutant defective for another specific enzyme of the ethylmalonyl-CoA pathway, mesaconyl-CoA hydratase (Mch), lost its ability for 3-hydroxypropionate-dependent growth. Interestingly, the Mch-deficient mutant was rescued either by introducing an additional ccr in-frame deletion that resulted in the blockage of an earlier step in the pathway or by heterologously expressing a gene encoding a thioesterase (YciA) that can act on several CoA intermediates of the ethylmalonyl-CoA pathway. The mch mutant expressing yciA metabolized only less than half of the 3-hydroxypropionate supplied, and over 50% of that carbon was recovered in the spent medium as free acids of the key intermediates mesaconyl-CoA and methylsuccinyl-CoA. A gradual increase in growth inhibition due to the blockage of consecutive steps of the ethylmalonyl-CoA pathway by gene deletions suggests that the growth defects were due to the titration of free CoA and depletion of the CoA pool in the cell rather than to detrimental effects arising from the accumulation of a specific metabolite. Recovery of carbon in mesaconate for the wild-type strain expressing yciA demonstrated that carbon flux through the ethylmalonyl-CoA pathway occurs during 3-hydroxypropionate-dependent growth. A possible role of the ethylmalonyl-CoA pathway is proposed that functions outside its known role in providing tricarboxylic acid intermediates during acetyl-CoA assimilation. IMPORTANCE Mutant analysis is an important tool utilized in metabolic studies to understand which role a particular pathway might have under certain growth conditions for a given organism. The importance of the enzyme and of the pathway in which it participates is discretely linked to the resulting phenotype observed after mutation of the corresponding gene. This work highlights the possibility of incorrectly interpreting mutant growth results that are based on studying a single unit (gene and encoded enzyme) of a metabolic pathway rather than the pathway in its entirety. This work also hints at the possibility of using an enzyme as a drug target although the enzyme may participate in a nonessential pathway and still be detrimental to the cell when inhibited.

scholarly journals Sulfolobus acidocaldariusTransports Pentoses via a Carbohydrate Uptake Transporter 2 (CUT2)-Type ABC Transporter and Metabolizes Them through the Aldolase-Independent Weimberg Pathway

2017 ◽  
Vol 84 (3) ◽  
Author(s):  
Michaela Wagner ◽  
Lu Shen ◽  
Andreas Albersmeier ◽  
Nienke van der Kolk ◽  
Sujin Kim ◽  
...  
Keyword(s):  
Abc Transporter ◽  
Abc Transporters ◽  
Cellulose Degradation ◽  
Growth Conditions ◽  
Sulfolobus Acidocaldarius ◽  
Transport Systems ◽  
Industrial Plant ◽  
Sugar Uptake ◽  
Content Type ◽  
Weimberg Pathway

ABSTRACTSulfolobusspp. possess a great metabolic versatility and grow heterotrophically on various carbon sources, such as different sugars and peptides. Known sugar transporters inArchaeapredominantly belong to ABC transport systems. Although several ABC transporters for sugar uptake have been characterized in the crenarchaeonSulfolobus solfataricus, only one homologue of these transporters, the maltose/maltooligomer transporter, could be identified in the closely relatedSulfolobus acidocaldarius. Comparison of the transcriptome ofS. acidocaldariusMW001 grown on peptides alone and peptides in the presence ofd-xylose allowed for the identification of the ABC transporter ford-xylose andl-arabinose transport and the gaining of deeper insights into pentose catabolism under the respective growth conditions. Thed-xylose/l-arabinose substrate binding protein (SBP) (Saci_2122) of the ABC transporter is unique inArchaeaand shares more similarity to bacterial SBPs of the carbohydrate uptake transporter-2 (CUT2) family than to any characterized archaeal one. The identified pentose transporter is the first CUT2 family ABC transporter analyzed in the domain ofArchaea. Single-gene deletion mutants of the ABC transporter subunits exemplified the importance of the transport system ford-xylose andl-arabinose uptake. Next to the transporter operon, enzymes of the aldolase-independent pentose catabolism branch were found to be upregulated in N-Z-Amine andd-xylose medium. The α-ketoglutarate semialdehyde dehydrogenase (KGSADH; Saci_1938) seemed not to be essential for growth on pentoses. However, the deletion mutant of the 2-keto-3-deoxyarabinoate/xylonate dehydratase (KDXD [also known as KDAD]; Saci_1939) was no longer able to catabolized-xylose orl-arabinose, suggesting the absence of the aldolase-dependent branch inS. acidocaldarius.IMPORTANCEThermoacidophilic microorganisms are emerging model organisms for biotechnological applications, as their optimal growth conditions resemble conditions used in certain biotechnologies such as industrial plant waste degradation. Because of its high genome stability,Sulfolobus acidocaldariusis especially suited as a platform organism for such applications. For use in (ligno)cellulose degradation, it was important to understand pentose uptake and metabolism inS. acidocaldarius. This study revealed that only the aldolase-independent Weimberg pathway is required for growth ofS. acidocaldariusMW001 ond-xylose andl-arabinose. Moreover,S. acidocaldariusemploys a CUT2 ABC transporter for pentose uptake, which is more similar to bacterial than to archaeal ABC transporters. The identification of pentose-inducible promoters will expedite the metabolic engineering ofS. acidocaldariusfor its development into a platform organism for (ligno)cellulose degradation.

scholarly journals Genus-Wide Assessment of Lignocellulose Utilization in the Extremely Thermophilic GenusCaldicellulosiruptorby Genomic, Pangenomic, and Metagenomic Analyses

2018 ◽  
Vol 84 (9) ◽  
Author(s):  
Laura L. Lee ◽  
Sara E. Blumer-Schuette ◽  
Javier A. Izquierdo ◽  
Jeffrey V. Zurawski ◽  
Andrew J. Loder ◽  
...  
Keyword(s):  
Microcrystalline Cellulose ◽  
Plant Biomass ◽  
Thermophilic Bacteria ◽  
Cellulose Degradation ◽  
Glycoside Hydrolases ◽  
Metagenomic Data ◽  
Lignocellulose Degradation ◽  
Sequence Information ◽  
Metagenomic Sequence ◽  
Content Type

ABSTRACTMetagenomic data from Obsidian Pool (Yellowstone National Park, USA) and 13 genome sequences were used to reassess genus-wide biodiversity for the extremely thermophilicCaldicellulosiruptor. The updated core genome contains 1,401 ortholog groups (average genome size for 13 species = 2,516 genes). The pangenome, which remains open with a revised total of 3,493 ortholog groups, encodes a variety of multidomain glycoside hydrolases (GHs). These include three cellulases with GH48 domains that are colocated in the glucan degradation locus (GDL) and are specific determinants for microcrystalline cellulose utilization. Three recently sequenced species,Caldicellulosiruptorsp. strain Rt8.B8 (renamed hereCaldicellulosiruptor morganii),Thermoanaerobacter cellulolyticusstrain NA10 (renamed hereCaldicellulosiruptor naganoensis), andCaldicellulosiruptorsp. strain Wai35.B1 (renamed hereCaldicellulosiruptor danielii), degraded Avicel and lignocellulose (switchgrass).C. morganiiwas more efficient thanCaldicellulosiruptor besciiin this regard and differed from the other 12 species examined, both based on genome content and organization and in the specific domain features of conserved GHs. Metagenomic analysis of lignocellulose-enriched samples from Obsidian Pool revealed limited new information on genus biodiversity. Enrichments yielded genomic signatures closely related to that ofCaldicellulosiruptor obsidiansis, but there was also evidence for other thermophilic fermentative anaerobes (Caldanaerobacter,Fervidobacterium,Caloramator, andClostridium). One enrichment, containing 89.8%Caldicellulosiruptorand 9.7%Caloramator, had a capacity for switchgrass solubilization comparable to that ofC. bescii. These results refine the known biodiversity ofCaldicellulosiruptorand indicate that microcrystalline cellulose degradation at temperatures above 70°C, based on current information, is limited to certain members of this genus that produce GH48 domain-containing enzymes.IMPORTANCEThe genusCaldicellulosiruptorcontains the most thermophilic bacteria capable of lignocellulose deconstruction, which are promising candidates for consolidated bioprocessing for the production of biofuels and bio-based chemicals. The focus here is on the extant capability of this genus for plant biomass degradation and the extent to which this can be inferred from the core and pangenomes, based on analysis of 13 species and metagenomic sequence information from environmental samples. Key to microcrystalline hydrolysis is the content of the glucan degradation locus (GDL), a set of genes encoding glycoside hydrolases (GHs), several of which have GH48 and family 3 carbohydrate binding module domains, that function as primary cellulases. Resolving the relationship between the GDL and lignocellulose degradation will inform efforts to identify more prolific members of the genus and to develop metabolic engineering strategies to improve this characteristic.

scholarly journals Spatial Distribution and Diverse Metabolic Functions of Lignocellulose-Degrading Uncultured Bacteria as Revealed by Genome-Centric Metagenomics

2018 ◽  
Vol 84 (18) ◽  
Author(s):  
Panagiotis G. Kougias ◽  
Stefano Campanaro ◽  
Laura Treu ◽  
Panagiotis Tsapekos ◽  
Andrea Armani ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Plant Biomass ◽  
Cellulose Degradation ◽  
Lignocellulose Degradation ◽  
Pig Manure ◽  
Carbohydrate Binding ◽  
Content Type ◽  
Polysaccharide Degradation ◽  
Carbohydrate Binding Modules ◽  
Metabolic Strategies

ABSTRACTThe mechanisms by which specific anaerobic microorganisms remain firmly attached to lignocellulosic material, allowing them to efficiently decompose organic matter, have yet to be elucidated. To circumvent this issue, microbiomes collected from anaerobic digesters treating pig manure and meadow grass were fractionated to separate the planktonic microbes from those adhered to lignocellulosic substrate. Assembly of shotgun reads, followed by a binning process, recovered 151 population genomes, 80 out of which were completely new and were not previously deposited in any database. Genome coverage allowed the identification of microbial spatial distribution in the engineered ecosystem. Moreover, a composite bioinformatic analysis using multiple databases for functional annotation revealed that uncultured members of theBacteroidetesandFirmicutesfollow diverse metabolic strategies for polysaccharide degradation. The structure of cellulosome inFirmicutesspecies can differ depending on the number and functional roles of carbohydrate-binding modules. In contrast, members of theBacteroidetesare able to adhere to and degrade lignocellulose due to the presence of multiple carbohydrate-binding family 6 modules in beta-xylosidase and endoglucanase proteins or S-layer homology modules in unknown proteins. This study combines the concept of variability in spatial distribution with genome-centric metagenomics, allowing a functional and taxonomical exploration of the biogas microbiome.IMPORTANCEThis work contributes new knowledge about lignocellulose degradation in engineered ecosystems. Specifically, the combination of the spatial distribution of uncultured microbes with genome-centric metagenomics provides novel insights into the metabolic properties of planktonic and firmly attached to plant biomass bacteria. Moreover, the knowledge obtained in this study enabled us to understand the diverse metabolic strategies for polysaccharide degradation in different species ofBacteroidetesandClostridiales. Even though structural elements of cellulosome were restricted toClostridialesspecies, our study identified a putative mechanism inBacteroidetesspecies for biomass decomposition, which is based on a gene cluster responsible for cellulose degradation, disaccharide cleavage to glucose, and transport to cytoplasm.

scholarly journals A Rhodobacter sphaeroides Protein Mechanistically Similar to Escherichia coli DksA Regulates Photosynthetic Growth

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Christopher W. Lennon ◽  
Kimberly C. Lemmer ◽  
Jessica L. Irons ◽  
Max I. Sellman ◽  
Timothy J. Donohue ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Structure Function ◽  
Rhodobacter Sphaeroides ◽  
Fatty Acid Content ◽  
Regulatory Protein ◽  
Growth Conditions ◽  
Globular Domain ◽  
Content Type ◽  
E Coli

ABSTRACTDksA is a global regulatory protein that, together with the alarmone ppGpp, is required for the “stringent response” to nutrient starvation in the gammaproteobacteriumEscherichia coliand for more moderate shifts between growth conditions. DksA modulates the expression of hundreds of genes, directly or indirectly. Mutants lacking a DksA homolog exhibit pleiotropic phenotypes in other gammaproteobacteria as well. Here we analyzed the DksA homolog RSP2654 in the more distantly relatedRhodobacter sphaeroides, an alphaproteobacterium. RSP2654 is 42% identical and similar in length toE. coliDksA but lacks the Zn finger motif of theE. coliDksA globular domain. Deletion of the RSP2654 gene results in defects in photosynthetic growth, impaired utilization of amino acids, and an increase in fatty acid content. RSP2654 complements the growth and regulatory defects of anE. colistrain lacking thedksAgene and modulates transcriptionin vitrowithE. coliRNA polymerase (RNAP) similarly toE. coliDksA. RSP2654 reduces RNAP-promoter complex stabilityin vitrowith RNAPs fromE. coliorR. sphaeroides, alone and synergistically with ppGpp, suggesting that even though it has limited sequence identity toE. coliDksA (DksAEc), it functions in a mechanistically similar manner. We therefore designate the RSP2654 protein DksARsp. Our work suggests that DksARsphas distinct and important physiological roles in alphaproteobacteria and will be useful for understanding structure-function relationships in DksA and the mechanism of synergy between DksA and ppGpp.IMPORTANCEThe role of DksA has been analyzed primarily in the gammaproteobacteria, in which it is best understood for its role in control of the synthesis of the translation apparatus and amino acid biosynthesis. Our work suggests that DksA plays distinct and important physiological roles in alphaproteobacteria, including the control of photosynthesis inRhodobacter sphaeroides. The study of DksARsp, should be useful for understanding structure-function relationships in the protein, including those that play a role in the little-understood synergy between DksA and ppGpp.

scholarly journals Microbial Functional Responses to Cholesterol Catabolism in Denitrifying Sludge

mSystems ◽  
2018 ◽  
Vol 3 (5) ◽  
Author(s):  
Sean Ting-Shyang Wei ◽  
Yu-Wei Wu ◽  
Tzong-Huei Lee ◽  
Yi-Shiang Huang ◽  
Cheng-Yu Yang ◽  
...  
Keyword(s):  
16S Rrna ◽  
De Novo ◽  
Anthropogenic Impacts ◽  
Sequence Similarity ◽  
Community Level ◽  
Model Organisms ◽  
Substrate Uptake ◽  
Functional Responses ◽  
Content Type ◽  
Rare Biosphere

ABSTRACTThe 2,3-secopathway, the pathway for anaerobic cholesterol degradation, has been established in the denitrifying betaproteobacteriumSterolibacterium denitrificans. However, knowledge of how microorganisms respond to cholesterol at the community level is elusive. Here, we applied mesocosm incubation and 16S rRNA sequencing to reveal that, in denitrifying sludge communities, three betaproteobacterial operational taxonomic units (OTUs) with low (94% to 95%) 16S rRNA sequence similarity toStl. denitrificansare cholesterol degraders and members of the rare biosphere. Metatranscriptomic and metabolite analyses show that these degraders adopt the 2,3-secopathway to sequentially catalyze the side chain and sterane of cholesterol and that two molybdoenzymes—steroid C25 dehydrogenase and 1-testosterone dehydrogenase/hydratase—are crucial for these bioprocesses, respectively. The metatranscriptome further suggests that these betaproteobacterial degraders display chemotaxis and motility toward cholesterol and that FadL-like transporters may be the key components for substrate uptake. Also, these betaproteobacteria are capable of transporting micronutrients and synthesizing cofactors essential for cellular metabolism and cholesterol degradation; however, the required cobalamin is possibly provided by cobalamin-de novo-synthesizing gamma-, delta-, and betaproteobacteria via the salvage pathway. Overall, our results indicate that the ability to degrade cholesterol in sludge communities is reserved for certain rare biosphere members and that C25 dehydrogenase can serve as a biomarker for sterol degradation in anoxic environments.IMPORTANCESteroids are ubiquitous and abundant natural compounds that display recalcitrance. Biodegradation via sludge communities in wastewater treatment plants is the primary removal process for steroids. To date, compared to studies for aerobic steroid degradation, the knowledge of anaerobic degradation of steroids has been based on only a few model organisms. Due to the increase of anthropogenic impacts, steroid inputs may affect microbial diversity and functioning in ecosystems. Here, we first investigated microbial functional responses to cholesterol, the most abundant steroid in sludge, at the community level. Our metagenomic and metatranscriptomic analyses revealed that the capacities for cholesterol approach, uptake, and degradation are unique traits of certain low-abundance betaproteobacteria, indicating the importance of the rare biosphere in bioremediation. Apparent expression of genes involved in cofactorde novosynthesis and salvage pathways suggests that these micronutrients play important roles for cholesterol degradation in sludge communities.

scholarly journals Bacillus velezensisWall Teichoic Acids Are Required for Biofilm Formation and Root Colonization

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
Zhihui Xu ◽  
Huihui Zhang ◽  
Xinli Sun ◽  
Yan Liu ◽  
Wuxia Yan ◽  
...  
Keyword(s):  
Plant Growth ◽  
Biofilm Formation ◽  
Root Colonization ◽  
Molecular Networks ◽  
Model Organisms ◽  
Bacillus Velezensis ◽  
Content Type ◽  
Plant Growth Promoting ◽  
Colonization Process ◽  
Growth Promoting

ABSTRACTRhizosphere colonization by plant growth-promoting rhizobacteria (PGPR) along plant roots facilitates the ability of PGPR to promote plant growth and health. Thus, an understanding of the molecular mechanisms of the root colonization process by plant-beneficialBacillusstrains is essential for the use of these strains in agriculture. Here, we observed that ansfpgene mutant of the plant growth-promoting rhizobacteriumBacillus velezensisSQR9 was unable to form normal biofilm architecture, and differential protein expression was observed by proteomic analysis. A minor wall teichoic acid (WTA) biosynthetic protein, GgaA, was decreased over 4-fold in the Δsfpmutant, and impairment of theggaAgene postponed biofilm formation and decreased cucumber root colonization capabilities. In addition, we provide evidence that the major WTA biosynthetic enzyme GtaB is involved in both biofilm formation and root colonization. The deficiency in biofilm formation of the ΔgtaBmutant may be due to an absence of UDP-glucose, which is necessary for the synthesis of biofilm matrix exopolysaccharides (EPS). These observations provide insights into the root colonization process by a plant-beneficialBacillusstrain, which will help improve its application as a biofertilizer.IMPORTANCEBacillus velezensisis a Gram-positive plant-beneficial bacterium which is widely used in agriculture. Additionally,Bacillusspp. are some of the model organisms used in the study of biofilms, and as such, the molecular networks and regulation systems of biofilm formation are well characterized. However, the molecular processes involved in root colonization by plant-beneficialBacillusstrains remain largely unknown. Here, we showed that WTAs play important roles in the plant root colonization process. The loss of thegtaBgene affects the ability ofB. velezensisSQR9 to sense plant polysaccharides, which are important environmental cues that trigger biofilm formation and colonization in the rhizosphere. This knowledge provides new insights into theBacillusroot colonization process and can help improve our understanding of plant-rhizobacterium interactions.

scholarly journals N-Acetylglucosamine-1-Phosphate Transferase, WecA, as a Validated Drug Target in Mycobacterium tuberculosis

2017 ◽  
Vol 61 (11) ◽  
Author(s):  
Stanislav Huszár ◽  
Vinayak Singh ◽  
Alica Polčicová ◽  
Peter Baráth ◽  
María Belén Barrio ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Drug Target ◽  
Functional Characterization ◽  
Drug Candidate ◽  
Content Type ◽  
Chemical Libraries ◽  
Whole Cells ◽  
Encoding Gene

ABSTRACT The mycobacterial phosphoglycosyltransferase WecA, which initiates arabinogalactan biosynthesis in Mycobacterium tuberculosis, has been proposed as a target of the caprazamycin derivative CPZEN-45, a preclinical drug candidate for the treatment of tuberculosis. In this report, we describe the functional characterization of mycobacterial WecA and confirm the essentiality of its encoding gene in M. tuberculosis by demonstrating that the transcriptional silencing of wecA is bactericidal in vitro and in macrophages. Silencing wecA also conferred hypersensitivity of M. tuberculosis to the drug tunicamycin, confirming its target selectivity for WecA in whole cells. Simple radiometric assays performed with mycobacterial membranes and commercially available substrates allowed chemical validation of other putative WecA inhibitors and resolved their selectivity toward WecA versus another attractive cell wall target, translocase I, which catalyzes the first membrane step in the biosynthesis of peptidoglycan. These assays and the mutant strain described herein will be useful for identifying potential antitubercular leads by screening chemical libraries for novel WecA inhibitors.

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