Showing papers by "Mel Rosenberg published in 1983"

Cell surface hydrophobicity of dental plaque microorganisms in situ.

Abstract: The cell surface hydrophobicity of bacteria obtained directly from human tooth surfaces was assayed by measuring their adherence to liquid hydrocarbons. Fresh samples of supragingival dental plaque were washed and dispersed in buffer. Adherence of the plaque microorganisms to hexadecane, octane, and xylene was tested turbidimetrically and by direct microscopic observation. The results clearly show that the vast majority of bacteria comprising dental plaque exhibit pronounced cell surface hydrophobicity. These data support the hypothesis that hydrophobic interactions play a major role in mediating bacterial adherence on tooth surfaces.

Bacterial adherence to hydrocarbons and to surfaces in the oral cavity

Abstract: L'hypothese selon laquelle cette adherence dependrait d'interactions hydrophobes est testee

Bacterial degradation of emulsan.

Abstract: Emulsan is a polyanionic heteropolysaccharide bioemulsifier produced by Acinetobacter calcoaceticus RAG-1. A mixed bacterial population was obtained by enrichment culture that was capable of degrading emulsan and using it as a carbon source. From this mixed culture, an emulsan-degrading bacterium, termed YUV-1, was isolated. Strain YUV-1 is an aerobic, gram-negative, non-spore-forming, rod-shaped bacterium which grows best in media containing yeast extract. When placed on preformed lawns of A. calcoaceticus RAG-1, strain YUV-1 produced translucent plaques which grew in size until the entire plate was covered. Plaque formation was due to solubilization of the emulsan capsule of RAG-1. Plaque formation was not observed on emulsan-negative mutants of RAG-1. As a consequence of the solubilization of the emulsan capsule, RAG-1 cells became more hydrophobic, as determined by adherence to hexadecane. Growth of YUV-1 on a medium containing yeast extract and emulsan was biphasic. During the initial 24 h, cell concentration increased 10-fold, but emulsan was not degraded; during the lag in growth (24 to 48 h), emulsan was inactivated and depolymerized but not consumed; during the second growth phase (48 to 70 h) the depolymerized emulsan products were consumed.

Bacterial Degradation ofEmulsan

Abstract: bioemulsifier producedby Acinetobacter calcoaceticus RAG-1.A mixedbacterial population was obtained byenrichment culture that was capable ofdegrading emulsan andusingitas a carbon source.Fromthis mixedculture, anemulsan-degrading bacterium, termed YUV-1,was isolated. Strain YUV-1isan aerobic, gram-negative, non-sporeforming, rod-shaped bacterium whichgrows bestinmediacontaining yeast extract. Whenplaced on preformed lawnsofA.calcoaceticus RAG-1,strain YUV-1produced translucent plaques which grew insize until theentire plate was covered. Plaque formation was duetosolubilization oftheemulsancapsule of RAG-1.Plaque formation was notobserved on emulsan-negative mutantsof RAG-1.Asa consequenceofthesolubilization oftheemulsan capsule, RAG-1 cells becamemore hydrophobic, as determined byadherence tohexadecane. GrowthofYUV-1on a mediumcontaining yeastextractandemulsan was biphasic. During theinitial 24h,cellconcentration increased 10-fold, butemulsan was notdegraded; during thelagingrowth (24to48h),emulsan was inactivated anddepolymerized butnotconsumed; during thesecond growth phase(48to70h) thedepolymerized emulsan products were consumed.

Microbial contamination by a medical carbon dioxide laser

Abstract: One of the advantages in using the carbon dioxide laser in medicine is the sterilization of the wound at the site of surgical intervention. In microbial studies, using the Sharplan Model 743 Medical Laser, we found substantial contamination of the area directly below the probe by viable bacteria and fungi. The levels of contamination varied from experiment to experiment, but were always substantial. The contamination is likely due to the stream of nitrogen gas emitted during and following laser irradiation in order to cool the lens. Following the implementation of several simple prophylactic procedures, including insertion of a filter on the end of the tube emitting the nitrogen gas, contamination by the gas stream was reduced to insignificant levels.