Regulatory Mechanism of Nicotine Degradation in Pseudomonas putida

ABSTRACT Nicotine, a toxic and addictive alkaloid from tobacco, is an environmental pollutant in areas near cigarette production facilities. Over the last decade, our group has studied, in depth, the pyrrolidine pathway of nicotine degradation in Pseudomonas putida S16. However, little is known regarding whole mechanism(s) regulating transcription of the nicotine degradation pathway gene cluster. In the present study, we comprehensively elucidate an overall view of the NicR2-mediated two-step mechanism regulating 3-succinoyl-pyridine (SP) biotransformation, which involves the association of free NicR2 with two promoters and the dissociation of NicR2 from the NicR2-promoter complex. NicR2 can bind to another promoter, Pspm, and regulate expression of the nicotine-degrading genes in the middle of nic2 gene cluster, which are not controlled by the previously reported Phsp promoter. We identified the function of the inverted repeat bases on the two promoters responsible for NicR2 binding and found out that the –35/–10 motif for RNA polymerase is overlapped by the NicR2 binding site. We clarify the exact role of 6-hydroxy-3-succinoyl-pyridine (HSP), which acts as an antagonist and may prevent binding of free NicR2 to the promoters but cannot release NicR2 from the promoters. Finally, a regulatory model is proposed, which consists of three parts: the interaction between NicR2 and two promoters (Pspm and Phsp), the interaction between NicR2 and two effectors (HSP and SP), and the interaction between NicR2 and RNA polymerase. IMPORTANCE We report the entire process underlying the NicR2 regulatory mechanism from association between free NicR2 and two promoters to dissociation of the NicR2-promoter complex. NicR2 can bind to another promoter, Pspm, which controls expression of nicotine-degrading genes that are not controlled by the Phsp promoter. We identified specific nucleotides of the Pspm promoter responsible for NicR2 binding. HSP was further demonstrated as an antagonist, which prevents the binding of NicR2 to the Pspm and Phsp promoters, by locking NicR2 in the derepression conformation. The competition between NicR2 and RNA polymerase is essential to initiate transcription of nicotine-degrading genes. This study extends our understanding of molecular mechanisms in biodegradation of environmental pollutants and toxicants.

Download Full-text

Molecular Deceleration Regulates Toxicant Release to Prevent Cell Damage in Pseudomonas putida S16 (DSM 28022)

mBio ◽

10.1128/mbio.02012-20 ◽

2020 ◽

Vol 11 (5) ◽

Author(s):

Hongzhi Tang ◽

Kunzhi Zhang ◽

Haiyang Hu ◽

Geng Wu ◽

Weiwei Wang ◽

...

Keyword(s):

Crystal Structure ◽

Pseudomonas Putida ◽

Molecular Mechanisms ◽

Cell Damage ◽

Amino Acid Residues ◽

Amine Oxidases ◽

Content Type ◽

Toxic Product ◽

Nicotine Degradation ◽

Cytotoxic Compounds

ABSTRACT The underlying molecular mechanisms of flavin-dependent amine oxidases remain relatively poorly understood, even though many of these enzymes have been reported. The nicotine oxidoreductase NicA2 is a crucial enzyme for the first step of nicotine degradation in Pseudomonas putida S16 (DSM 28022). Here, we present the crystal structure of a ternary complex comprising NicA2 residues 21 to 482, flavin adenine dinucleotide (FAD), and nicotine at 2.25 Å resolution. Unlike other, related structures, NicA2 does not have an associated diacyl glycerophospholipid, wraps its substrate more tightly, and has an intriguing exit passage in which nine bulky amino acid residues occlude the release of its toxic product, pseudooxynicotine (PN). The replacement of these bulky residues by amino acids with small side chains effectively increases the catalytic turnover rate of NicA2. Our results indicate that the passage in wild-type NicA2 effectively controls the rate of PN release and thus prevents its rapid intracellular accumulation. It gives ample time for PN to be converted to less-harmful substances by downstream enzymes such as pseudooxynicotine amine oxidase (Pnao) before its accumulation causes cell damage or even death. The temporal metabolic regulation mode revealed in this study may shed light on the production of cytotoxic compounds. IMPORTANCE Flavin-dependent amine oxidases have received extensive attention because of their importance in drug metabolism, Parkinson’s disease, and neurotransmitter catabolism. However, the underlying molecular mechanisms remain relatively poorly understood. Here, combining the crystal structure of NicA2 (an enzyme in the first step of the bacterial nicotine degradation pathway in Pseudomonas putida S16 (DSM 28022)), biochemical analysis, and mutant construction, we found an intriguing exit passage in which bulky amino acid residues occlude the release of the toxic product of NicA2, in contrast to other, related structures. The selective product exportation register for NicA2 has proven to be beneficial to cell growth. Those seeking to produce cytotoxic compounds could greatly benefit from the use of such an export register mechanism.

Download Full-text

A SilencedvanAGene Cluster on a Transferable Plasmid Caused an Outbreak of Vancomycin-Variable Enterococci

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00286-16 ◽

2016 ◽

Vol 60 (7) ◽

pp. 4119-4127 ◽

Cited By ~ 16

Author(s):

Audun Sivertsen ◽

Torunn Pedersen ◽

Kjersti Wik Larssen ◽

Kåre Bergh ◽

Torunn Gresdal Rønning ◽

...

Keyword(s):

Gene Cluster ◽

Molecular Mechanisms ◽

Genetic Difference ◽

Brain Heart Infusion ◽

Broad Host Range ◽

S1 Nuclease ◽

Content Type ◽

Transcription Profiles

ABSTRACTWe report an outbreak of vancomycin-variablevanA+enterococci (VVE) able to escape phenotypic detection by current guidelines and demonstrate the molecular mechanisms forin vivoswitching into vancomycin resistance and horizontal spread of thevanAcluster. Forty-eightvanA+Enterococcus faeciumisolates and oneEnterococcus faecalisisolate were analyzed for clonality with pulsed-field gel electrophoresis (PFGE), and theirvanAgene cluster compositions were assessed by PCR and whole-genome sequencing of six isolates. The susceptible VVE strains were cultivated in brain heart infusion broth containing vancomycin at 8 μg/ml forin vitrodevelopment of resistant VVE. The transcription profiles of susceptible VVE and their resistant revertants were assessed using quantitative reverse transcription-PCR. Plasmid content was analyzed with S1 nuclease PFGE and hybridizations. Conjugative transfer ofvanAwas assessed by filter mating. The only genetic difference between thevanAclusters of susceptible and resistant VVE was an ISL3-family element upstream ofvanHAX, which silencedvanHAXgene transcription in susceptible VVE. Furthermore, the VVE had an insertion of IS1542betweenorf2andvanRthat attenuated the expression ofvanHAX. Growth of susceptible VVE occurred after 24 to 72 h of exposure to vancomycin due to excision of the ISL3-family element. ThevanAgene cluster was located on a transferable broad-host-range plasmid also detected in outbreak isolates with different pulsotypes, including oneE. faecalisisolate. Horizontally transferable silencedvanAable to escape detection and revert into resistance during vancomycin therapy represents a new challenge in the clinic. Genotypic testing of invasive vancomycin-susceptible enterococci byvanA-PCR is advised.

Download Full-text

Evolution of Chemical Diversity in Echinocandin Lipopeptide Antifungal Metabolites

Eukaryotic Cell ◽

10.1128/ec.00076-15 ◽

2015 ◽

Vol 14 (7) ◽

pp. 698-718 ◽

Cited By ~ 25

Author(s):

Qun Yue ◽

Li Chen ◽

Xiaoling Zhang ◽

Kuan Li ◽

Jingzu Sun ◽

...

Keyword(s):

Gene Cluster ◽

Incomplete Lineage Sorting ◽

Gene Clusters ◽

Antifungal Drugs ◽

Chemical Diversity ◽

Specific Gene ◽

Gene Trees ◽

Content Type ◽

Antifungal Metabolites ◽

Pathway Gene

ABSTRACTThe echinocandins are a class of antifungal drugs that includes caspofungin, micafungin, and anidulafungin. Gene clusters encoding most of the structural complexity of the echinocandins provided a framework for hypotheses about the evolutionary history and chemical logic of echinocandin biosynthesis. Gene orthologs among echinocandin-producing fungi were identified. Pathway genes, including the nonribosomal peptide synthetases (NRPSs), were analyzed phylogenetically to address the hypothesis that these pathways represent descent from a common ancestor. The clusters share cooperative gene contents and linkages among the different strains. Individual pathway genes analyzed in the context of similar genes formed unique echinocandin-exclusive phylogenetic lineages. The echinocandin NRPSs, along with the NRPS from theinpgene cluster inAspergillus nidulansand its orthologs, comprise a novel lineage among fungal NRPSs. NRPS adenylation domains from different species exhibited a one-to-one correspondence between modules and amino acid specificity that is consistent with models of tandem duplication and subfunctionalization. Pathway gene trees and Ascomycota phylogenies are congruent and consistent with the hypothesis that the echinocandin gene clusters have a common origin. The disjunct Eurotiomycete-Leotiomycete distribution appears to be consistent with a scenario of vertical descent accompanied by incomplete lineage sorting and loss of the clusters from most lineages of theAscomycota. We present evidence for a single evolutionary origin of the echinocandin family of gene clusters and a progression of structural diversification in two fungal classes that diverged approximately 290 to 390 million years ago. Lineage-specific gene cluster evolution driven by selection of new chemotypes contributed to diversification of the molecular functionalities.

Download Full-text

Taxis of Pseudomonas putida F1 toward Phenylacetic Acid Is Mediated by the Energy Taxis Receptor Aer2

Applied and Environmental Microbiology ◽

10.1128/aem.03895-12 ◽

2013 ◽

Vol 79 (7) ◽

pp. 2416-2423 ◽

Cited By ~ 21

Author(s):

Rita A. Luu ◽

Benjamin J. Schneider ◽

Christie C. Ho ◽

Vasyl Nesteryuk ◽

Stacy E. Ngwesse ◽

...

Keyword(s):

Pseudomonas Putida ◽

Phenylacetic Acid ◽

Environmental Pollutants ◽

Bacterial Chemotaxis ◽

Degradation Pathway ◽

Content Type ◽

E Coli ◽

Energy Taxis ◽

System A

ABSTRACTThe phenylacetic acid (PAA) degradation pathway is a widely distributed funneling pathway for the catabolism of aromatic compounds, including the environmental pollutants styrene and ethylbenzene. However, bacterial chemotaxis to PAA has not been studied. The chemotactic strainPseudomonas putidaF1 has the ability to utilize PAA as a sole carbon and energy source. We identified a putative PAA degradation gene cluster (paa) inP. putidaF1 and demonstrated that PAA serves as a chemoattractant. The chemotactic response was induced during growth with PAA and was dependent on PAA metabolism. A functionalcheAgene was required for the response, indicating that PAA is sensed through the conserved chemotaxis signal transduction system. AP. putidaF1 mutant lacking the energy taxis receptor Aer2 was deficient in PAA taxis, indicating that Aer2 is responsible for mediating the response to PAA. The requirement for metabolism and the role of Aer2 in the response indicate thatP. putidaF1 uses energy taxis to detect PAA. We also revealed that PAA is an attractant forEscherichia coli; however, a mutant lacking a functional Aer energy receptor had a wild-type response to PAA in swim plate assays, suggesting that PAA is detected through a different mechanism inE. coli. The role of Aer2 as an energy taxis receptor provides the potential to sense a broad range of aromatic growth substrates as chemoattractants. Since chemotaxis has been shown to enhance the biodegradation of toxic pollutants, the ability to sense PAA gradients may have implications for the bioremediation of aromatic hydrocarbons that are degraded via the PAA pathway.

Download Full-text

A Novel Membrane Protein, VanJ, Conferring Resistance to Teicoplanin

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05869-11 ◽

2012 ◽

Vol 56 (4) ◽

pp. 1784-1796 ◽

Cited By ~ 24

Author(s):

Gabriela Novotna ◽

Chris Hill ◽

Karen Vincent ◽

Chang Liu ◽

Hee-Jeon Hong

Keyword(s):

Membrane Protein ◽

Gene Cluster ◽

Molecular Mechanisms ◽

Bacterial Resistance ◽

Streptomyces Coelicolor ◽

Biosynthetic Gene Cluster ◽

Glycopeptide Antibiotics ◽

Content Type ◽

Peptidoglycan Biosynthesis ◽

New Family

ABSTRACTBacterial resistance to the glycopeptide antibiotic teicoplanin shows some important differences from the closely related compound vancomycin. They are currently poorly understood but may reflect significant differences in the mode of action of each antibiotic.Streptomyces coelicolorpossesses avanRSJKHAXgene cluster that when expressed confers resistance to both vancomycin and teicoplanin. The resistance to vancomycin is mediated by the enzymes encoded byvanKHAX, but not byvanJ. vanHAXeffect a reprogramming of peptidoglycan biosynthesis, which is considered to be generic, conferring resistance to all glycopeptide antibiotics. Here, we show thatvanKHAXare not in fact required for teicoplanin resistance inS. coelicolor, which instead is mediated solely byvanJ. vanJis shown to encode a membrane protein oriented with its C-terminal active site exposed to the extracytoplasmic space. VanJ also confers resistance to the teicoplanin-like antibiotics ristocetin and A47934 and to a broad range of semisynthetic teicoplanin derivatives, but not generally to antibiotics or semisynthetic derivatives with vancomycin-like structures.vanJhomologues are found ubiquitously in streptomycetes and includestaPfrom theStreptomyces toyocaensisA47934 biosynthetic gene cluster. While overexpression ofstaPalso conferred resistance to teicoplanin, similar expression of othervanJhomologues (SCO2255, SCO7017, and SAV5946) did not. ThevanJandstaPorthologues, therefore, appear to represent a subset of a larger protein family whose members have acquired specialist roles in antibiotic resistance. Future characterization of the divergent enzymatic activity within this new family will contribute to defining the molecular mechanisms important for teicoplanin activity and resistance.

Download Full-text

ArcD1 and ArcD2 Arginine/Ornithine Exchangers Encoded in the Arginine Deiminase Pathway Gene Cluster of Lactococcus lactis

Journal of Bacteriology ◽

10.1128/jb.00526-15 ◽

2015 ◽

Vol 197 (22) ◽

pp. 3545-3553 ◽

Cited By ~ 12

Author(s):

Elke E. E. Noens ◽

Michał B. Kaczmarek ◽

Monika Żygo ◽

Juke S. Lolkema

Keyword(s):

Gene Cluster ◽

Lactococcus Lactis ◽

Physiological Function ◽

Arginine Deiminase ◽

Growth Media ◽

Growth Enhancement ◽

Resting Cells ◽

Gene Encoding ◽

Content Type ◽

Pathway Gene

ABSTRACTThe arginine deiminase (ADI) pathway gene cluster inLactococcus lactiscontains two copies of a gene encoding anl-arginine/l-ornithine exchanger, thearcD1andarcD2genes. The physiological function of ArcD1 and ArcD2 was studied by deleting the two genes. Deletion ofarcD1resulted in loss of the growth advantage observed in the presence of highl-arginine in different growth media. Uptake ofl-arginine andl-ornithine by resting cells was reduced to the low level observed for an ArcD1/ArcD2 double deletion mutant. Deletion of thearcD2gene did not affect the growth enhancement, and uptake activities were slightly reduced. Nevertheless, recombinant expression of ArcD2 in the ArcD1/ArcD2 double mutant did recover the growth advantage. Kinetic characterization of ArcD1 and ArcD2 showed high affinities for bothl-arginine andl-ornithine (Kmin the micromolar range). A difference between the two transporters was the significantly lower affinity of ArcD2 for the cationic amino acidsl-ornithine,l-lysine, andl-histidine. In contrast, the affinity of ArcD2 was higher for the neutral amino acidl-alanine. Moreover, ArcD2 efficiently translocatedl-alanine, while ArcD1 did not. Both transporters revealed affinities in the mM range for agmatine, cadaverine, histamine, and putrescine. These amines bind but are not translocated. It is concluded that ArcD1 is the mainl-arginine/l-ornithine exchanger in the ADI pathway and that ArcD2 is not functionally expressed in the media used. ArcD2 is proposed to function together with thearcTgene that encodes a putative transaminase and is found adjacent to thearcD2gene.IMPORTANCEThe arginine deiminase (ADI) pathway gene cluster inLactococcus lactiscontains two copies of a gene encoding anl-arginine/l-ornithine exchanger, thearcD1andarcD2genes. The physiological function of ArcD1 and ArcD2 was studied by deleting the two genes. It is concluded that ArcD1 is the mainl-arginine/l-ornithine exchanger in the ADI pathway. ArcD2 is proposed to function as al-arginine/l-alanine exchanger in a pathway together with thearcTgene, which is found adjacent to thearcD2gene in the ADI gene cluster.

Download Full-text

Novel Metabolic Pathway for N-Methylpyrrolidone Degradation in Alicycliphilus sp. Strain BQ1

Applied and Environmental Microbiology ◽

10.1128/aem.02136-17 ◽

2017 ◽

Vol 84 (1) ◽

Cited By ~ 3

Author(s):

Claudia Julieta Solís-González ◽

Lilianha Domínguez-Malfavón ◽

Martín Vargas-Suárez ◽

Itzel Gaytán ◽

Miguel Ángel Cevallos ◽

...

Keyword(s):

Gene Cluster ◽

Metabolic Pathway ◽

Molecular Mechanisms ◽

Skin Irritation ◽

Enzymatic Activities ◽

Acid Oxidase ◽

Amino Acid Oxidase ◽

Content Type ◽

Semialdehyde Dehydrogenase ◽

Succinate Semialdehyde

ABSTRACTThe molecular mechanisms underlying the biodegradation ofN-methylpyrrolidone (NMP), a widely used industrial solvent that produces skin irritation in humans and is teratogenic in rats, are unknown.Alicycliphilussp. strain BQ1 degrades NMP. By studying a transposon-tagged mutant unable to degrade NMP, we identified a six-gene cluster (nmpABCDEF) that is transcribed as a polycistronic mRNA and encodes enzymes involved in NMP biodegradation.nmpAand the transposon-affected genenmpBencode anN-methylhydantoin amidohydrolase that transforms NMP to γ-N-methylaminobutyric acid; this is metabolized by an amino acid oxidase (NMPC), either by demethylation to produce γ-aminobutyric acid (GABA) or by deamination to produce succinate semialdehyde (SSA). If GABA is produced, the activity of a GABA aminotransferase (GABA-AT), not encoded in thenmpgene cluster, is needed to generate SSA. SSA is transformed by a succinate semialdehyde dehydrogenase (SSDH) (NMPF) to succinate, which enters the Krebs cycle. The abilities to consume NMP and to utilize it for growth were complemented in the transposon-tagged mutant by use of thenmpABCDgenes. Similarly,Escherichia coliMG1655, which has two SSDHs but is unable to grow in NMP, acquired these abilities after functional complementation with these genes. In wild-type (wt) BQ1 cells growing in NMP, GABA was not detected, but SSA was present at double the amount found in cells growing in Luria-Bertani medium (LB), suggesting that GABA is not an intermediate in this pathway. Moreover,E. coliGABA-AT deletion mutants complemented withnmpABCDgenes retained the ability to grow in NMP, supporting the possibility that γ-N-methylaminobutyric acid is deaminated to SSA instead of being demethylated to GABA.IMPORTANCEN-Methylpyrrolidone is a cyclic amide reported to be biodegradable. However, the metabolic pathway and enzymatic activities for degrading NMP are unknown. By developing molecular biology techniques forAlicycliphilussp. strain BQ1, an environmental bacterium able to grow in NMP, we identified a six-gene cluster encoding enzymatic activities involved in NMP degradation. These findings set the basis for the study of new enzymatic activities and for the development of biotechnological processes with potential applications in bioremediation.

Download Full-text

Genome-Wide Assessment of Streptococcus agalactiae Genes Required for Survival in Human Whole Blood and Plasma

Infection and Immunity ◽

10.1128/iai.00357-20 ◽

2020 ◽

Vol 88 (10) ◽

Author(s):

Luchang Zhu ◽

Prasanti Yerramilli ◽

Layne Pruitt ◽

Matthew Ojeda Saavedra ◽

Concepcion C. Cantu ◽

...

Keyword(s):

Streptococcus Agalactiae ◽

Whole Blood ◽

Molecular Mechanisms ◽

Insertion Site ◽

Shikimate Pathway ◽

Bacterial Survival ◽

Content Type ◽

Human Whole Blood ◽

Pathway Gene ◽

Genome Wide

ABSTRACT Streptococcus agalactiae (group B streptococcus, or GBS) is a common cause of bacteremia and sepsis in newborns, pregnant women, and immunocompromised patients. The molecular mechanisms used by GBS to survive and proliferate in blood are not well understood. Here, using a highly virulent GBS strain and transposon-directed insertion site sequencing (TraDIS), we performed genome-wide screens to discover novel GBS genes required for bacterial survival in human whole blood and plasma. The screen identified 85 and 41 genes that are required for GBS growth in whole blood and plasma, respectively. A common set of 29 genes was required in both whole blood and plasma. Targeted gene deletion confirmed that (i) genes encoding methionine transporter (metP) and manganese transporter (mtsA) are crucial for GBS survival in whole blood and plasma, (ii) gene W903_1820, encoding a small multidrug export family protein, contributes significantly to GBS survival in whole blood, (iii) the shikimate pathway gene aroA is essential for GBS growth in whole blood and plasma, and (iv) deletion of srr1, encoding a fibrinogen-binding adhesin, increases GBS survival in whole blood. Our findings provide new insight into the GBS-host interactions in human blood.

Download Full-text

The Novel Transcriptional Regulator LmbU Promotes Lincomycin Biosynthesis through Regulating Expression of Its Target Genes in Streptomyces lincolnensis

Journal of Bacteriology ◽

10.1128/jb.00447-17 ◽

2017 ◽

Vol 200 (2) ◽

Cited By ~ 16

Author(s):

Bingbing Hou ◽

Yanwei Lin ◽

Haizhen Wu ◽

Meijin Guo ◽

Hrvoje Petkovic ◽

...

Keyword(s):

Gene Cluster ◽

Target Genes ◽

Regulatory Mechanism ◽

Transcriptional Regulator ◽

Gene Clusters ◽

Saccharopolyspora Erythraea ◽

Transcriptional Analysis ◽

Biosynthetic Gene ◽

Content Type ◽

Streptomyces Lincolnensis

ABSTRACT Lincomycin A is a clinically important antimicrobial agent produced by Streptomyces lincolnensis . In this study, a new regulator designated LmbU (GenBank accession no. ABX00623.1) was identified and characterized to regulate lincomycin biosynthesis in S. lincolnensis wild-type strain NRRL 2936. Both inactivation and overexpression of lmbU resulted in significant influences on lincomycin production. Transcriptional analysis and in vivo neomycin resistance (Neo r ) reporter assays demonstrated that LmbU activates expression of the lmbA , lmbC , lmbJ , and lmbW genes and represses expression of the lmbK and lmbU genes. Electrophoretic mobility shift assays (EMSAs) demonstrated that LmbU can bind to the regions upstream of the lmbA and lmbW genes through the consensus and palindromic sequence 5′-CGCCGGCG-3′. However, LmbU cannot bind to the regions upstream of the lmbC , lmbJ , lmbK , and lmbU genes as they lack this motif. These data indicate a complex transcriptional regulatory mechanism of LmbU. LmbU homologues are present in the biosynthetic gene clusters of secondary metabolites of many other actinomycetes. Furthermore, the LmbU homologue from Saccharopolyspora erythraea (GenBank accession no. WP_009944629.1) also binds to the regions upstream of lmbA and lmbW , which suggests widespread activity for this regulator. LmbU homologues have no significant structural similarities to other known cluster-situated regulators (CSRs), which indicates that they belong to a new family of regulatory proteins. In conclusion, the present report identifies LmbU as a novel transcriptional regulator and provides new insights into regulation of lincomycin biosynthesis in S. lincolnensis . IMPORTANCE Although lincomycin biosynthesis has been extensively studied, its regulatory mechanism remains elusive. Here, a novel regulator, LmbU, which regulates transcription of its target genes in the lincomycin biosynthetic gene cluster ( lmb gene cluster) and therefore promotes lincomycin biosynthesis, was identified in S. lincolnensis strain NRRL 2936. Importantly, we show that this new regulatory element is relatively widespread across diverse actinomycetes species. In addition, our findings provide a new strategy for improvement of yield of lincomycin through manipulation of LmbU, and this approach could also be evaluated in other secondary metabolite gene clusters containing this regulatory protein.

Download Full-text

Metabolism of Four α-Glycosidic Linkage-Containing Oligosaccharides by Bifidobacterium breve UCC2003

Applied and Environmental Microbiology ◽

10.1128/aem.01775-13 ◽

2013 ◽

Vol 79 (20) ◽

pp. 6280-6292 ◽

Cited By ~ 31

Author(s):

Kerry Joan O'Connell ◽

Mary O'Connell Motherway ◽

John O'Callaghan ◽

Gerald F. Fitzgerald ◽

R. Paul Ross ◽

...

Keyword(s):

Gene Cluster ◽

Molecular Mechanisms ◽

Functional Genomic ◽

Adjacent Gene ◽

Glycosidic Linkage ◽

Carbohydrate Utilization ◽

Content Type ◽

Bifidobacterium Breve

ABSTRACTMembers of the genusBifidobacteriumare common inhabitants of the gastrointestinal tracts of humans and other mammals, where they ferment many diet-derived carbohydrates that cannot be digested by their hosts. To extend our understanding of bifidobacterial carbohydrate utilization, we investigated the molecular mechanisms by which 11 strains ofBifidobacterium brevemetabolize four distinct α-glucose- and/or α-galactose-containing oligosaccharides, namely, raffinose, stachyose, melibiose, and melezitose. Here we demonstrate that allB. brevestrains examined possess the ability to utilize raffinose, stachyose, and melibiose. However, the ability to metabolize melezitose was not common to allB. brevestrains tested. Transcriptomic and functional genomic approaches identified a gene cluster dedicated to the metabolism of α-galactose-containing carbohydrates, while an adjacent gene cluster, dedicated to the metabolism of α-glucose-containing melezitose, was identified in strains that are able to use this carbohydrate.

Download Full-text