PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-6 (6)
 

Clipboard (0)
None

Select a Filter Below

Journals
Authors
more »
Year of Publication
Document Types
1.  Adherence to Streptococci facilitates Fusobacterium nucleatum integration into an oral microbial community 
Microbial Ecology  2011;63(3):532-542.
The development of multispecies oral microbial communities involves complex intra- and interspecies interactions at various levels. The ability to adhere to the resident bacteria or the biofilm matrix and overcome community resistance are among the key factors that determine whether a bacterium can integrate into a community. In this study, we focus on community integration of Fusobacterium nucleatum, a prevalent Gram-negative oral bacterial species that is considered an important member of the oral community due to its ability to adhere to Gram-positive as well as Gram-negative species. This interaction with a variety of different species is thought to facilitate the establishment of multispecies oral microbial community. However, the majority of experiments thus far has focused on the physical adherence between two species as measured by in vitro co-aggregation assays, while the community-based effects on the integration of F. nucleatum into multispecies microbial community remains to be investigated. In this study, we demonstrated using an established in vitro mice oral microbiota (O-mix) that the viability of F. nucleatum was significantly reduced upon addition to the O-mix due to cell contact-dependent induction of hydrogen peroxide (H2O2) production by oral community. Interestingly, this inhibitory effect was significantly alleviated when F. nucleatum was allowed to adhere to its known interacting partner species (such as Streptococcus sanguinis) prior to addition. Furthermore, this aggregate formation-dependent protection was absent in the F. nucleatum mutant strain ΔFn1526 that is unable to bind to a number of Gram-positive species. More importantly, this protective effect was also observed during integration of F. nucleatum into a human salivary microbial community (S-mix). These results support the idea that by adhering to other oral microbes, such as streptococci, F. nucleatum is able to mask the surface components that are recognized by H2O2 producing oral community members. This evasion strategy prevents detection by antagonistic oral bacteria and allows integration into the developing oral microbial community.
doi:10.1007/s00248-011-9989-2
PMCID: PMC3313671  PMID: 22202886
coaggregation; Fusobacterium nucleatum; microbial flora; oral cavity; community resistance
2.  Selective Membrane Disruption: Mode of Action of C16G2, a Specifically Targeted Antimicrobial Peptide ▿ 
The specifically targeted antimicrobial peptide (STAMP) C16G2 was developed to target the cariogenic oral pathogen Streptococcus mutans. Because the design of this peptide was novel, we sought to better understand the mechanism through which it functioned. Compared to antimicrobial peptides (AMPs) with wide spectra of activity, the STAMP C16G2 has demonstrated specificity for S. mutans in a mixed-culture environment, resulting in the complete killing of S. mutans while having minimal effect on the other streptococci. In the current study, we sought to further confirm the selectivity of C16G2 and also compare its membrane activity to that of melittin B, a classical toxic AMP, in order to determine the STAMP's mechanism of cell killing. Disruption of S. mutans cell membranes by C16G2 was demonstrated by increased SYTOX green uptake and ATP efflux from the cells similar to those of melittin B. Treatment with C16G2 also resulted in a loss of membrane potential as measured by DiSC(3)5 fluorescence. In comparison, the individual moieties of C16G2 demonstrated no specificity and limited antimicrobial activity compared to those of the STAMP C16G2. The data suggest that C16G2 has a mechanism of action similar to that of traditional AMPs and kills S. mutans through disruption of the cell membrane, allowing small molecules to leak out of the cell, which is followed by a loss of membrane potential and cell death. Interestingly, this membrane activity is rapid and potent against S. mutans, but not other noncariogenic oral streptococci.
doi:10.1128/AAC.00342-11
PMCID: PMC3122425  PMID: 21518845
3.  Fusobacterium nucleatum Outer Membrane Proteins Fap2 and RadD Induce Cell Death in Human Lymphocytes▿  
Infection and Immunity  2010;78(11):4773-4778.
Bacterially induced cell death in human lymphocytes is an important virulence factor for pathogenic bacteria. Previously discovered mechanisms of bacterially induced cell death are predominantly based on the transfer of bacterial proteins to the target host cell, such as the toxins secreted through type I, II, and VI secretion systems or effector proteins injected through type III, IV, and Vb secretion systems. Here, we report a mechanism employed by the Gram-negative oral pathogen Fusobacterium nucleatum for cell death induction of human lymphocytes via two outer membrane proteins (OMPs), Fap2 and RadD, which share regions homologous to autotransporter secretion systems (type Va secretion systems). Genetic and physiological studies established that inactivation of the two OMPs led to significantly reduced ability to trigger cell death in Jurkat cells, while the corresponding double mutant was almost completely attenuated. Additional biochemical and molecular analyses demonstrated that cell-free F. nucleatum membranes are sufficient to induce cell death in Jurkat cells, suggesting that no active process or effector protein transfer was necessary to induce eukaryotic cell death.
doi:10.1128/IAI.00567-10
PMCID: PMC2976331  PMID: 20823215
4.  The Fusobacterium nucleatum Outer Membrane Protein RadD Is an Arginine-Inhibitable Adhesin Required for Inter-Species Adherence and the Structured Architecture of Multi-Species Biofilm 
Molecular microbiology  2008;71(1):35-47.
Summary
A defining characteristic of the suspected periodontal pathogen Fusobacterium nucleatum is its ability to adhere to a plethora of oral bacteria. This distinguishing feature is suggested to play an important role in oral biofilm formation and pathogenesis, with fusobacteria proposed to serve as central “bridging organisms” in the architecture of the oral biofilm bringing together species which would not interact otherwise. Previous studies indicate that these bacterial interactions are mediated by galactose- or arginine-inhibitable adhesins although genetic evidence for the role and nature of these proposed adhesins remains elusive. To characterize these adhesins at the molecular level, the genetically transformable F. nucleatum strain ATCC 23726 was screened for adherence properties, and arginine inhibitable adhesion was evident, while galactose-inhibitable adhesion was not detected. Six potential arginine binding proteins were isolated from the membrane fraction of F. nucleatum ATCC 23726 and identified via mass spectroscopy as members of the outer membrane family of proteins in F. nucleatum. Inactivation of the genes encoding these six candidates for arginine-inhibitable adhesion and two additional homologues revealed that only a mutant derivative carrying an insertion in Fn1526 (now designated as radD) demonstrated significantly decreased co-aggregation with representatives of the Gram-positive “early oral colonizers”. Lack of the 350 kDa outer membrane protein encoded by radD resulted in the failure to form the extensive structured biofilm observed with the parent strain when grown in the presence of Streptococcus sanguinis ATCC 10556. These findings indicate that radD is responsible for arginine-inhibitable adherence of F. nucleatum and provides definitive molecular evidence that F. nucleatum adhesins play a vital role in inter-species adherence and multispecies biofilm formation.
doi:10.1111/j.1365-2958.2008.06503.x
PMCID: PMC2741168  PMID: 19007407
Fusobacterium nucleatum; RadD. Arginine; Adhesin; Biofilm; Co-aggregation
5.  Bacterial Succession in a Petroleum Land Treatment Unit 
Bacterial community dynamics were investigated in a land treatment unit (LTU) established at a site contaminated with highly weathered petroleum hydrocarbons in the C10 to C32 range. The treatment plot, 3,000 cubic yards of soil, was supplemented with nutrients and monitored weekly for total petroleum hydrocarbons (TPH), soil water content, nutrient levels, and aerobic heterotrophic bacterial counts. Weekly soil samples were analyzed with 16S rRNA gene terminal restriction fragment (TRF) analysis to monitor bacterial community structure and dynamics during bioremediation. TPH degradation was rapid during the first 3 weeks and slowed for the remainder of the 24-week project. A sharp increase in plate counts was reported during the first 3 weeks, indicating an increase in biomass associated with petroleum degradation. Principal components analysis of TRF patterns revealed a series of sample clusters describing bacterial succession during the study. The largest shifts in bacterial community structure began as the TPH degradation rate slowed and the bacterial cell counts decreased. For the purpose of analyzing bacterial dynamics, phylotypes were generated by associating TRFs from three enzyme digests with 16S rRNA gene clones. Two phylotypes associated with Flavobacterium and Pseudomonas were dominant in TRF patterns from samples during rapid TPH degradation. After the TPH degradation rate slowed, four other phylotypes gained dominance in the community while Flavobacterium and Pseudomonas phylotypes decreased in abundance. These data suggest that specific phylotypes of bacteria were associated with the different phases of petroleum degradation in the LTU.
doi:10.1128/AEM.70.3.1777-1786.2004
PMCID: PMC368334  PMID: 15006804
6.  16S Ribosomal DNA Terminal Restriction Fragment Pattern Analysis of Bacterial Communities in Feces of Rats Fed Lactobacillus acidophilus NCFM 
16S ribosomal DNA terminal restriction fragment patterns from rat fecal samples were analyzed to track the dynamics of Lactobacillus acidophilus NCFM and discern bacterial populations that changed during feeding with NCFM. Lactobacillus johnsonii and Ruminococcus flavefaciens were tentatively identified as such bacterial populations. The presence of L. johnsonii was confirmed by isolation from feces.
doi:10.1128/AEM.67.4.1935-1939.2001
PMCID: PMC92815  PMID: 11282651

Results 1-6 (6)