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1.  Transcriptional Responses of Treponema denticola to Other Oral Bacterial Species 
PLoS ONE  2014;9(2):e88361.
The classic organization by Socransky and coworkers categorized the oral bacteria of the subgingival plaque into different complexes. Treponema denticola, Porphyromonas gingivalis and Tannerella forsythia are grouped into the red complex that is highly correlated with periodontal disease. Socransky's work closely associates red with orange complex species such as Fusobacterium nucleatum and Prevotella intermedia but not with members of the other complexes. While the relationship between species contained by these complexes is in part supported by their ability to physically attach to each other, the physiological consequences of these interactions and associations are less clear. In this study, we employed T. denticola as a model organism to analyze contact-dependent responses to interactions with species belonging to the same complex (P. gingivalis and T. forsythia), the closely associated orange complex (using F. nucleatum and P. intermedia as representatives) and the unconnected yellow complex (using Streptococcus sanguinis and S. gordonii as representatives). RNA was extracted from T. denticola alone as well as after pairwise co-incubation for 5 hrs with representatives of the different complexes, and the respective gene expression profiles were determined using microarrays. Numerous genes related to motility, metabolism, transport, outer membrane and hypothetical proteins were differentially regulated in T. denticola in the presence of the tested partner species. Further analysis revealed a significant overlap in the affected genes and we identified a general response to the presence of other species, those specific to two of the three complexes as well as individual complexes. Most interestingly, many predicted major antigens (e.g. flagella, Msp, CTLP) were suppressed in responses that included red complex species indicating that the presence of the most closely associated species induces immune-evasive strategies. In summary, the data presented here provide an in-depth understanding of the transcriptional responses triggered by contact-dependent interactions between microorganisms inhabiting the periodontal pocket.
doi:10.1371/journal.pone.0088361
PMCID: PMC3914990  PMID: 24505483
2.  Effects of Exopolysaccharide Production on Liquid Vegetative Growth, Stress Survival and Stationary Phase Recovery in Myxococcus xanthus 
Journal of microbiology (Seoul, Korea)  2012;50(2):10.1007/s12275-012-1349-5.
Exopolysaccharide (EPS) of Myxococcus xanthus is a well-regulated cell surface component. In addition to its known functions for social motility and fruiting body formation on solid surfaces, EPS has also been proposed to play a role in multi-cellular clumping in liquid medium, though this phenomenon has not been well studied. In this report, we confirmed that M. xanthus clumps formed in liquid were correlated with EPS levels and demonstrated that the EPS encased cell clumps exhibited biofilm-like structures. The clumps protected the cells at physiologically relevant EPS concentrations, while cells lacking EPS exhibited significant reduction in long-term viability and resistance to stressful conditions. However, excess EPS production was counterproductive to vegetative growth and viable cell recovery declined in extended late stationary phase as cells became trapped in the matrix of clumps. Therefore, optimal EPS production by M. xanthus is important for normal physiological functions in liquid.
doi:10.1007/s12275-012-1349-5
PMCID: PMC3819231  PMID: 22538652
Myxococcus xanthus; exopolysaccharide; vegetative growth; stress survival; stationary phase recovery
3.  HIV Infection is associated with compositional and functional shifts in the rectal mucosal microbiota 
Microbiome  2013;1:26.
Background
Regardless of infection route, the intestine is the primary site for HIV-1 infection establishment and results in significant mucosal CD4+ T lymphocyte depletion, induces an inflammatory state that propagates viral dissemination, facilitates microbial translocation, and fosters establishment of one of the largest HIV reservoirs. Here we test the prediction that HIV infection modifies the composition and function of the mucosal commensal microbiota.
Results
Rectal mucosal microbiota were collected from human subjects using a sponge-based sampling methodology. Samples were collected from 20 HIV-positive men not receiving combination anti-retroviral therapy (cART), 20 HIV-positive men on cART and 20 healthy, HIV-negative men. Microbial composition of samples was analyzed using barcoded 16S Illumina deep sequencing (85,900 reads per sample after processing). Microbial metagenomic information for the samples was imputed using the bioinformatic tools PICRUST and HUMAnN. Microbial composition and imputed function in HIV-positive individuals not receiving cART was significantly different from HIV-negative individuals. Genera including Roseburia, Coprococcus, Ruminococcus, Eubacterium, Alistipes and Lachnospira were depleted in HIV-infected subjects not receiving cART, while Fusobacteria, Anaerococcus, Peptostreptococcus and Porphyromonas were significantly enriched. HIV-positive subjects receiving cART exhibited similar depletion and enrichment for these genera, but were of intermediate magnitude and did not achieve statistical significance. Imputed metagenomic functions, including amino acid metabolism, vitamin biosynthesis, and siderophore biosynthesis differed significantly between healthy controls and HIV-infected subjects not receiving cART.
Conclusions
HIV infection was associated with rectal mucosal changes in microbiota composition and imputed function that cART failed to completely reverse. HIV infection was associated with depletion of some commensal species and enrichment of a few opportunistic pathogens. Many imputed metagenomic functions differed between samples from HIV-negative and HIV-positive subjects not receiving cART, possibly reflecting mucosal metabolic changes associated with HIV infection. Such functional pathways may represent novel interventional targets for HIV therapy if normalizing the microbial composition or functional activity of the microbiota proves therapeutically useful.
doi:10.1186/2049-2618-1-26
PMCID: PMC3971626  PMID: 24451087
HIV; Microbiome; Metagenome; Mucosa
4.  Integrative analysis of the microbiome and metabolome of the human intestinal mucosal surface reveals exquisite inter-relationships 
Microbiome  2013;1:17.
Background
Consistent compositional shifts in the gut microbiota are observed in IBD and other chronic intestinal disorders and may contribute to pathogenesis. The identities of microbial biomolecular mechanisms and metabolic products responsible for disease phenotypes remain to be determined, as do the means by which such microbial functions may be therapeutically modified.
Results
The composition of the microbiota and metabolites in gut microbiome samples in 47 subjects were determined. Samples were obtained by endoscopic mucosal lavage from the cecum and sigmoid colon regions, and each sample was sequenced using the 16S rRNA gene V4 region (Illumina-HiSeq 2000 platform) and assessed by UPLC mass spectroscopy. Spearman correlations were used to identify widespread, statistically significant microbial-metabolite relationships. Metagenomes for identified microbial OTUs were imputed using PICRUSt, and KEGG metabolic pathway modules for imputed genes were assigned using HUMAnN. The resulting metabolic pathway abundances were mostly concordant with metabolite data. Analysis of the metabolome-driven distribution of OTU phylogeny and function revealed clusters of clades that were both metabolically and metagenomically similar.
Conclusions
The results suggest that microbes are syntropic with mucosal metabolome composition and therefore may be the source of and/or dependent upon gut epithelial metabolites. The consistent relationship between inferred metagenomic function and assayed metabolites suggests that metagenomic composition is predictive to a reasonable degree of microbial community metabolite pools. The finding that certain metabolites strongly correlate with microbial community structure raises the possibility of targeting metabolites for monitoring and/or therapeutically manipulating microbial community function in IBD and other chronic diseases.
doi:10.1186/2049-2618-1-17
PMCID: PMC3971612  PMID: 24450808
Microbiome; Metabolome; Inter-omic analysis
5.  DNA Builds and Strengthens the Extracellular Matrix in Myxococcus xanthus Biofilms by Interacting with Exopolysaccharides 
PLoS ONE  2012;7(12):e51905.
One intriguing discovery in modern microbiology is the extensive presence of extracellular DNA (eDNA) within biofilms of various bacterial species. Although several biological functions have been suggested for eDNA, including involvement in biofilm formation, the detailed mechanism of eDNA integration into biofilm architecture is still poorly understood. In the biofilms formed by Myxococcus xanthus, a Gram-negative soil bacterium with complex morphogenesis and social behaviors, DNA was found within both extracted and native extracellular matrices (ECM). Further examination revealed that these eDNA molecules formed well organized structures that were similar in appearance to the organization of exopolysaccharides (EPS) in ECM. Biochemical and image analyses confirmed that eDNA bound to and colocalized with EPS within the ECM of starvation biofilms and fruiting bodies. In addition, ECM containing eDNA exhibited greater physical strength and biological stress resistance compared to DNase I treated ECM. Taken together, these findings demonstrate that DNA interacts with EPS and strengthens biofilm structures in M. xanthus.
doi:10.1371/journal.pone.0051905
PMCID: PMC3530553  PMID: 23300576
6.  Transcriptional Profiles of Treponema denticola in Response to Environmental Conditions 
PLoS ONE  2010;5(10):e13655.
The periodontal pathogen T. denticola resides in a stressful environment rife with challenges, the human oral cavity. Knowledge of the stress response capabilities of this invasive spirochete is currently very limited. Whole genome expression profiles in response to different suspected stresses including heat shock, osmotic downshift, oxygen and blood exposure were examined. Most of the genes predicted to encode conserved heat shock proteins (HSPs) were found to be induced under heat and oxygen stress. Several of these HSPs also seem to be important for survival in hypotonic solutions and blood. In addition to HSPs, differential regulation of many genes encoding metabolic proteins, hypothetical proteins, transcriptional regulators and transporters was observed in patterns that could betoken functional associations. In summary, stress responses in T. denticola exhibit many similarities to the corresponding stress responses in other organisms but also employ unique components including the induction of hypothetical proteins.
doi:10.1371/journal.pone.0013655
PMCID: PMC2965109  PMID: 21048920
7.  Induction of Protective Immunity against Murine Gammaherpesvirus 68 Infection in the Absence of Viral Latency▿  
Journal of Virology  2009;84(5):2453-2465.
Human gammaherpesviruses, Epstein-Barr virus, and human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus are important pathogens associated with diseases, including lymphomas and other malignancies. Murine gammaherpesvirus 68 (MHV-68) is used as an experimental model system to study the host immune control of infection and explore novel vaccine strategies based on latency-deficient live viruses. We studied the properties and the potential of a recombinant MHV-68 (AC-RTA) in which the genes required for persistent infection were replaced by a constitutively expressed viral transcription activator, RTA, which dictates the virus to lytic replication. After intranasal infection of mice, replication of AC-RTA in the lung was attenuated, and no AC-RTA virus or viral DNA was detected in the isolated splenocytes, indicating a lack of latency in the spleen. Infection of the AC-RTA virus elicited both cellular immune responses and virus-specific IgG at a level comparable to that elicited by infection of the wild-type virus. Importantly, vaccination of AC-RTA was able to protect mice against subsequent challenge by the wild-type MHV-68. AC-RTA provides a vaccine strategy for preventing infection of human gammaherpesviruses. Furthermore, our results suggest that immunity to the major latent antigens is not required for protection.
doi:10.1128/JVI.01543-09
PMCID: PMC2820913  PMID: 20015983
8.  Enhancement of Antimicrobial Activity against Pseudomonas aeruginosa by Coadministration of G10KHc and Tobramycin▿  
Antimicrobial Agents and Chemotherapy  2006;50(11):3833-3838.
Pseudomonas aeruginosa is a common opportunistic human pathogen that is associated with life-threatening acute infections and chronic airway colonization during cystic fibrosis. Previously, we converted the wide-spectrum antimicrobial peptide novispirin G10 into a selectively-targeted antimicrobial peptide (STAMP), G10KHc. Compared to novispirin G10, the STAMP had an enhanced ability to kill Pseudomonas mendocina. In this study, we explored the activity of G10KHc against P. aeruginosa. G10KHc was found to be highly active (as active as tobramycin) against P. aeruginosa clinical isolates. Most interestingly, we observed a synergistic-like enhancement in killing activity when biofilms and planktonic cultures of P. aeruginosa were cotreated with G10KHc and tobramycin. The data indicate that the mechanism of enhanced activity may involve increased tobramycin uptake due to G10KHc-mediated cell membrane disruption. These results suggest that G10KHc may be useful against P. aeruginosa during acute and chronic infection states, especially when it is coadministered with tobramycin.
doi:10.1128/AAC.00509-06
PMCID: PMC1635211  PMID: 16940063
9.  N-Glycans on Nipah Virus Fusion Protein Protect against Neutralization but Reduce Membrane Fusion and Viral Entry 
Journal of Virology  2006;80(10):4878-4889.
Nipah virus (NiV) is a deadly emerging paramyxovirus. The NiV attachment (NiV-G) and fusion (NiV-F) envelope glycoproteins mediate both syncytium formation and viral entry. Specific N-glycans on paramyxovirus fusion proteins are generally required for proper conformational integrity and biological function. However, removal of individual N-glycans on NiV-F had little negative effect on processing or fusogenicity and has even resulted in slightly increased fusogenicity. Here, we report that in both syncytium formation and viral entry assays, removal of multiple N-glycans on NiV-F resulted in marked increases in fusogenicity (>5-fold) but also resulted in increased sensitivity to neutralization by NiV-F-specific antisera. The mechanism underlying the hyperfusogenicity of these NiV-F N-glycan mutants is likely due to more-robust six-helix bundle formation, as these mutants showed increased fusion kinetics and were more resistant to neutralization by a fusion-inhibitory reagent based on the C-terminal heptad repeat region of NiV-F. Finally, we demonstrate that the fusogenicities of the NiV-F N-glycan mutants were inversely correlated with the relative avidities of NiV-F's interactions with NiV-G, providing support for the attachment protein “displacement” model of paramyxovirus fusion. Our results indicate that N-glycans on NiV-F protect NiV from antibody neutralization, suggest that this “shielding” role comes together with limiting cell-cell fusion and viral entry efficiencies, and point to the mechanisms underlying the hyperfusogenicity of these N-glycan mutants. These features underscore the varied roles that N-glycans on NiV-F play in the pathobiology of NiV entry but also shed light on the general mechanisms of paramyxovirus fusion with host cells.
doi:10.1128/JVI.80.10.4878-4889.2006
PMCID: PMC1472062  PMID: 16641279
10.  Murine Gammaherpesvirus 68 Open Reading Frame 45 Plays an Essential Role during the Immediate-Early Phase of Viral Replication 
Journal of Virology  2005;79(8):5129-5141.
Murine gammaherpesvirus 68 (MHV-68) has been developed as a model for the human gammaherpesviruses Epstein-Barr virus and human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus (HHV-8/KSHV), which are associated with several types of human diseases. Open reading frame 45 (ORF45) is conserved among the members of the Gammaherpesvirinae subfamily and has been suggested to be a virion tegument protein. The repression of ORF45 expression by small interfering RNAs inhibits MHV-68 viral replication. However, the gene product of MHV-68 ORF45 and its function have not yet been well characterized. In this report, we show that MHV-68 ORF45 is a phosphorylated nuclear protein. We constructed an ORF45-null MHV-68 mutant virus (45STOP) by the insertion of translation termination codons into the portion of the gene encoding the N terminus of ORF45. We demonstrated that the ORF45 protein is essential for viral gene expression immediately after the viral genome enters the nucleus. These defects in viral replication were rescued by providing ORF45 in trans or in an ORF45-null revertant (45STOP.R) virus. Using a transcomplementation assay, we showed that the function of ORF45 in viral replication is conserved with that of its KSHV homologue. Finally, we found that the C-terminal 23 amino acids that are highly conserved among the Gammaherpesvirinae subfamily are critical for the function of ORF45 in viral replication.
doi:10.1128/JVI.79.8.5129-5141.2005
PMCID: PMC1069521  PMID: 15795297

Results 1-10 (10)