ABSTRACT: A case study to investigate the relationship between antibacterial activity and quorum sensing mechanisms was carried out
on a sponge-associated bacterium with remarkable biological activities: Pseudoalteromonas sp. NJ6-3-1. The dependence of active substance production on cell density was studied under various growth conditions. Bacteria
NJ6-3-1 was found to start producing antibacterial compounds only when cell density reached the threshold value of OD630 = 0.4. To simulate the competitive real marine environment, NJ6-3-1 at low cell density (OD630 value below the required threshold value) was co-cultured with the terrestrial bacterium Staphylococcus aureus. Antibacterial activity assays indicated the existence of some signal molecules in the metabolites of S. aureus that could induce NJ6-3-1 to produce antibacterial substances even at low cell density. Three diketopiperazines (DKPs) as
metabolites and potential autoinducers of NJ6-3-1 were synthesized and co-cultured with low density NJ6-3-1. The antibacterial
activity assay showed that one of these DKPs—cyclo-(l-Phe-l-Val)—was the autoinducer and could indeed induce NJ6-3-1 to produce antibacterial substances under low cell density. Our
results thus provide preliminary support to the hypothesis that the antibacterial activity of NJ6-3-1 is controlled by the
quorum sensing system in both an intra-species and an inter-species manner.
KeywordsQuorum sensing–Sponge-associated bacterium–Antibacterial activity–Diketoperazines
Annals of Microbiology 04/2012; 61(2):247-255. · 0.69 Impact Factor
ABSTRACT: The high sensitive immunoassay of protein cancer biomarkers is achieved by using of peroxidase-mimicking DNAzyme heavily functionalized gold nanoparticles as catalytic probe.
Chemical Communications 11/2009; · 6.17 Impact Factor
ABSTRACT: We chose a sponge-associated marine-bacterium Pseudoalteromonas piscicida NJ6-3-1 to study whether its antibacterial activity were regulated by quorum sensing.
We studied the relationship between the antibacterial activity and bacterial density under various growth conditions. To simulate the natural competitive environment, we monitored the antibacterial activity at low cell density when the species were co-cultured with Staphylococcus aureus.
Antibacterial activity correlated closely with cell density. Marine bacterium NJ6-3-1 started producing antibacterial compounds when cell density reached the threshold value of OD(630) = 0.4. Some signal molecules existing in the metabolites of S. aureus could induce the production of antibacterial substance by marine-bacteria NJ6-3-1 even cell density below the required threshold.
The results provide preliminary evidence to support the hypothesis that the antibacterial activity of NJ6-3-1 was regulated by the quorum sensing system of intraspecies and interspecies.
ACTA MICROBIOLOGICA SINICA 05/2008; 48(4):545-50.
ABSTRACT: A new method based on accelerated solvent extraction (ASE) followed by a reliable high-performance liquid chromatography-diode array detector (HPLC-DAD) and positive ion electrospray-time of flight mass spectrometry (ESI-TOF/MS) analysis has been developed for the characterization and quantification of four major saponins in extracts of the seeds of Aesculus chinensis Bunge (semen aesculi). The saponins escin Ia, escin Ib, isoescin Ia and isoescin Ib were extracted from seeds of A. chinesis Bunge via ASE, and the operational parameters of ASE were optimized, such as extraction solvent, extraction temperature, static extraction time and extraction cycles. The optimized procedure employed 70% MeOH as extraction solvent, 120 degrees C of extraction temperature, 7 min of static extraction time, 60% flush volume and the extraction recoveries of the four compounds were nearly to 100% for two cycles. The HPLC conditions are as follows: SinoChrom ODS BP C18 (4.6 mm x 200 mm, 5 microm) column, acetonitrile and 0.10% phosphoric acid solution as mobile phase, flow rate is 1.0 mL min(-1), detection length of UV is 203 nm, injection volume is 10 microL. The results indicated that the developed HPLC method is simple, sensitive and reliable for the determination of four major saponins in seeds of A. chinesis Bunge with a good linearity (r2 > 0.9994), precision (relative standard deviation (R.S.D.) < 1.5%) and the recovery ranges of 95.2-97.3%. The limits of detection (LOD) of the four compounds were in the range of 0.40-0.75 microg mL(-1). This assay can be readily utilized as a quality control method for semen aesculi and other related medicinal plants.
Analytica chimica acta 08/2007; 596(2):273-80. · 4.31 Impact Factor