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Persistence of Streptococcus mutans in Stationary-Phase Batch Cultures and Biofilms. John A. Renye Jr., 2004.Streptococcus mutans is a member of oral plaque biofilms and is considered the major etiological agent of dental caries . We have characterized the survival of S . mutans strain UA159 in both batch cultures and biofilms . Bacteria grown in batch cultures in a chemically defined medium, FMC, containing an excess of glucose or sucrose caused the pH to decrease to 4.0 at the entry into stationary phase, and they survived for about 3 days . Survival was extended up to 11 days when the medium contained a limiting concentration of glucose or sucrose that was depleted by the time the bacteria reached stationary phase . Sugar-limited cultures maintained a pH of 7.0 throughout stationary phase . Their survival was shortened to 3 days by the addition of exogenous lactic acid at the entry into stationary phase . Sugar starvation did not lead to comparable survival in biofilms . Although the pH remained at 7.0, bacteria could no longer be cultured from biofilms 4 days after the imposition of glucose or sucrose starvation; BacLight staining results did not agree with survival results based on culturability . In both batch cultures and biofilms, survival could be extended by the addition of 0.5% mucin to the medium . Batch survival increased to an average of 26 (±8) days, and an average of 2.7 x 105 CFU per chamber were still present in biofilms that were starved of sucrose for 12 days . Construction and Synchronization of dnaA Temperature-Sensitive Mutants of Streptomyces. Li-Fong Lee, 2002.Temperature-sensitive mutants of Streptomyces defective in initiation of chromosome replication were created by in vitro site-directed mutagenesis in the dnaA gene followed by gene replacement . When they were shifted to 39°C replication in the mutants ceased in about 90 min but resumed on return to 30°C . This allowed manipulations to achieve replication synchronization . Production of Novel Tetrahydroxyfuranyl Fatty Acids from  -Linolenic Acid by Clavibacter sp . Strain ALA2.Masashi Hosokawa, 2003.Previously, it was reported that a newly isolated microbial culture, Clavibacter sp . strain ALA2, produced trihydroxy unsaturated fatty acids, diepxoy bicyclic fatty acids, and tetrahydroxyfuranyl fatty acids (THFAs) from linoleic acid (C . T . Hou, J . Am . Oil Chem . Soc . 73:1359-1362, 1996; C . T . Hou and R . J . Forman III, J . Ind . Microbiol . Biotechnol . 24:275-276, 2000; C . T . Hou, H . Gardner, and W . Brown, J . Am . Oil Chem . Soc . 75:1483-1487, 1998; C . T . Hou, H . W . Gardner, and W . Brown, J . Am . Oil Chem . Soc . 78:1167-1169, 2001) . In this study, we found that Clavibacter sp . strain ALA2 produced novel THFAs, including 13,16-dihydroxy-12-THFA, 15-epoxy-9(Z)-octadecenoic acid (13,16-dihydroxy-THFA), and 7,13,16-trihydroxy-12, 15-epoxy-9(Z)-octadecenoic acid (7,13,16-trihydroxy-THFA), from -linolenic acid (9,12,15-octadecatrienoic acid) . The chemical structures of these products were determined by gas chromatography-mass spectrometry and proton and 13C nuclear magnetic resonance analyses . The optimum incubation temperature was 30°C for production of both hydroxy-THFAs . 13,16-Dihydroxy-THFA was detected after 2 days of incubation, and the concentration reached 45 mg/50 ml after 7 days of incubation; 7,13,16-trihydroxy-THFA was not detected after 2 days of incubation, but the concentration reached 9 mg/50 ml after 7 days of incubation . The total yield of both 13,16-dihydroxy-THFA and 7,13,16-trihydroxy-THFA was 67% (wt/wt) after 7 days of incubation at 30°C and 200 rpm . In previous studies, it was reported that Clavibacter sp . strain ALA2 oxidized the C-7, C-12, C-13, C-16, and C-17 positions of linoleic acid (n-6) into hydroxy groups . In this case, the bond between the C-16 and C-17 carbon atoms is saturated . In
-linolenic acid (n-3), however, the bond between the C-16 and C-17 carbon atoms is unsaturated . It seems that enzymes of strain ALA2 oxidized the C-12-C-13 and C-16-C-17 double bonds into dihydroxy groups first and then converted them to hydroxy-THFAs .
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