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Impact of Quorum Sensing and Tropodithietic Acid Production on the Exometabolome of Phaeobacter inhibens.

ABSTRACT: Microbial interactions shape ecosystem diversity and chemistry through production and exchange of organic compounds, but the impact of regulatory mechanisms on production and release of these exometabolites is largely unknown. We studied the extent and nature of impact of two signaling molecules, tropodithietic acid (TDA) and the quorum sensing molecule acyl homoserine lactone (AHL) on the exometabolome of the model bacterium Phaeobacter inhibens DSM 17395, a member of the ubiquitous marine Roseobacter group. Exometabolomes of the wild type, a TDA and a QS (AHL-regulator) negative mutant were analyzed via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Based on a total of 996 reproducibly detected molecular masses, exometabolomes of the TDA and QS negative mutant were ∼70% dissimilar to each other, and ∼90 and ∼60% dissimilar, respectively, to that of the wild type. Moreover, at any sampled growth phase, 40-60% of masses detected in any individual exometabolome were unique to that strain, while only 10-12% constituted a shared "core exometabolome." Putative annotation revealed exometabolites of ecological relevance such as vitamins, amino acids, auxins, siderophore components and signaling compounds with different occurrence patterns in the exometabolomes of the three strains. Thus, this study demonstrates that signaling molecules, such as AHL and TDA, extensively impact the composition of bacterial exometabolomes with potential consequences for species interactions in microbial communities.

SUBMITTER: Srinivas S

PROVIDER: S-EPMC9253639 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Tropodithietic acid production in Phaeobacter gallaeciensis is regulated by N-acyl homoserine lactone-mediated quorum sensing.

Project description:The production of N-acyl homoserine lactones (AHLs) is widely distributed within the marine Roseobacter clade, and it was proposed that AHL-mediated quorum sensing (QS) is one of the most common cell-to-cell communication mechanisms in roseobacters. The traits regulated by AHL-mediated QS are yet not known for members of the Roseobacter clade, but production of the antibiotic tropodithietic acid (TDA) was supposed to be controlled by AHL-mediated QS in Phaeobacter spp. We describe here for the first time the functional role of luxR and luxI homologous genes of an organism of the Roseobacter clade, i.e., pgaR and pgaI in Phaeobacter gallaeciensis. Our results demonstrate that the AHL synthase gene pgaI is responsible for production of N-3-hydroxydecanoylhomoserine lactone (3OHC(10)-HSL). Insertion mutants of pgaI and pgaR are both deficient in TDA biosynthesis and the formation of a yellow-brown pigment when grown in liquid marine broth medium. This indicates that in P. gallaeciensis the production of both secondary metabolites is controlled by AHL-mediated QS. Quantitative real-time PCR showed that the transcription level of tdaA, which encodes an essential transcriptional regulator for TDA biosynthesis, decreased 28- and 51-fold in pgaI and pgaR genetic backgrounds, respectively. These results suggest that both the response regulator PgaR and the 3OHC(10)-HSL produced by PgaI induce expression of tdaA, which in turn positively regulates expression of the tda genes. Moreover, we confirmed that TDA can also act as autoinducer in P. gallaeciensis, as previously described for Silicibacter sp. strain TM1040, but only in the presence of the response regulator PgaR.

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Influence of Iron on Production of the Antibacterial Compound Tropodithietic Acid and Its Noninhibitory Analog in Phaeobacter inhibens.

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Dual Function of Tropodithietic Acid as Antibiotic and Signaling Molecule in Quorum Sensing

Project description:The marine bacterium Phaeobacter inhibens produces tropodithietic acid (TDA), a broad-spectrum antibiotic and anticancer agent. TDA allows P. inhibens to antagonize other bacteria, including several pathogens, and eukaryotes. Since recently antibiotics are also discussed to function as intermicrobial signals. Here we show that ~10% of the genes of P. inhibens are strongly influenced by N-acyl-homoserine lactone (AHL) mediated quorum sensing (QS), switching the bacterium’s life style from attached to free-living. In an AHL negative mutant of P. inhibens subinhibitory concentrations of TDA caused the same regulatory effect as the AHL. This demonstrates that bacteria can produce antibiotic compounds not only as weapons, but also to substitute their endogenous AHL molecule in QS. The dual function of TDA probably supports the QS system to accelerate regulatory processes and points to a so far neglected role of antibiotics at subinhibitory concentrations in the environment and in microbial interactions.

2016-03-15 | GSE79173 | GEO

Dual Function of Tropodithietic Acid as Antibiotic and Signaling Molecule in Quorum Sensing

Project description:The marine bacterium Phaeobacter inhibens produces tropodithietic acid (TDA), a broad-spectrum antibiotic and anticancer agent. TDA allows P. inhibens to antagonize other bacteria, including several pathogens, and eukaryotes. Since recently antibiotics are also discussed to function as intermicrobial signals. Here we show that ~10% of the genes of P. inhibens are strongly influenced by N-acyl-homoserine lactone (AHL) mediated quorum sensing (QS), switching the bacteriumâs life style from attached to free-living. In an AHL negative mutant of P. inhibens subinhibitory concentrations of TDA caused the same regulatory effect as the AHL. This demonstrates that bacteria can produce antibiotic compounds not only as weapons, but also to substitute their endogenous AHL molecule in QS. The dual function of TDA probably supports the QS system to accelerate regulatory processes and points to a so far neglected role of antibiotics at subinhibitory concentrations in the environment and in microbial interactions. Comparison of whole transcriptomes of wildytype, quorum sensing mutants (pgaI and pgaR) and pgaI grown supplemented with subinhibitory concentration of the antibiotic TDA. RNA isolated in the late exponential growth phase. 4 biological replicates investigated for each strain.

2016-03-15 | E-GEOD-79173 | biostudies-arrayexpress

Morphological Heterogeneity and Attachment of Phaeobacter inhibens.

Project description:The Roseobacter clade is a key group of bacteria in the ocean exhibiting diverse metabolic repertoires and a wide range of symbiotic life-styles. Many Roseobacters possess remarkable capabilities of attachment to both biotic and abiotic surfaces. When attached to each other, these bacteria form multi-cellular structures called rosettes. Phaeobacter inhibens, a well-studied Roseobacter, exhibits various cell sizes and morphologies that are either associated with rosettes or occur as single cells. Here we describe the distribution of P. inhibens morphologies and rosettes within a population. We detect an N-acetylglucosamine-containing polysaccharide on the poles of some cells and at the center of all rosettes. We demonstrate that rosettes are formed by the attachment of individual cells at the polysaccharide-containing pole rather than by cell division. Finally, we show that P. inhibens attachment to abiotic surfaces is hindered by the presence of DNA from itself, but not from other bacteria. Taken together, our findings demonstrate that cell adhesiveness is likely to play a significant role in the life cycle of P. inhibens as well as other Roseobacters.

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