Limitations in obtaining sufficient specimens and difficulties in extracting high quality DNA from environmental samples have impeded understanding of the structure of microbial communities. In this study, multiple displacement amplification (MDA) using phi29 polymerase was applied to overcome these hindrances. Optimization of the reaction conditions for amplification of the bacterial genome and evaluation of the MDA product were performed using cyanobacterium Synechocystis sp. strain PCC6803. An 8-h MDA reaction yielded a sufficient quantity of DNA from an initial amount of 0.4 ng, which is equivalent to approximately 10(5) cells. Uniform amplification of genes randomly selected from the cyanobacterial genome was confirmed by real-time polymerase chain reaction. The metagenome from bacteria associated with scleractinian corals was used for whole-genome amplification using phi29 polymerase to analyse the microbial diversity. Unidentified bacteria with less than 93% identity to the closest 16S rDNA sequences deposited in DNA Data Bank of Japan were predominantly detected from the coral-associated bacterial community before and after the MDA procedures. Sequencing analysis indicated that alpha-Proteobacteria was the dominant group in Pocillopora damicornis. This study demonstrates that MDA techniques are efficient for genome wide investigation to understand the actual microbial diversity in limited bacterial samples.

Using a metagenome library constructed from a bacterial associated with a marine sponge Hyrtios erecta, we identified a novel esterase that belongs to the SGNH hydrolase superfamily of esterases. The substrate specificity of EstHE1 was determined using p-nitrophenyl (pNP) ester (C2: acetate, C4: butylate, C6: caproate, C12: laurate, C16: palmitate). EstHE1 exhibited activity against C2 (5.6 U/mg), C4 (5.1 U/mg), and C6 (2.8 U/mg) substrates. The optimal temperature for EstHE1 esterase activity of the pNP acetate substrate was 40 degrees C, and EstHE1 retained 60% of its enzymatic activity in the 30-50 degrees C range. This esterase showed moderate thermostability, retaining 58% of its activity even after preincubation for 12 h at 40 degrees C. EstHE1 also maintained activity in high concentrations of NaCl, indicating that this esterase is salt-tolerant. Thus, EstHE1 has the thermal stability and salt tolerance necessary for use as an industrial enzyme.

A new method for disinfection of microorganisms by electrochemically regenerated periodate was developed. Oxidation of iodate to periodate was observed at 1.25 V versus a silver/silver chloride electrode in a cyclic voltammogram of potassium iodate. When 1.25 V was applied in 1.0 mM potassium iodate, approximately 4-log inactivation of Escherichia coli was observed in 30 min.Iodine-based disinfectant has been used for many years in the medical field and for potable water disinfection where municipal water treatment is not reliable. The mechanism of antimicrobial disinfection is based on the fact that iodine is a strong oxidant (1,6,7,17). Iodine-based disinfectants are more stable chemically and have a more acceptable taste than chlorine-based disinfectants, which makes them useful for disinfection in field work. Euthyroid individuals can be treated safely with iodine-containing solutions at a residual concentration less than 1.0 mg/liter, even for a long period of time (4, 5). However, excess iodine ingestion can be deleterious to human health. The major health effect of excess iodine ingestion is the development of thyroid diseases (2). Therefore, removal of excess iodine using activated carbon is required to ensure safe levels of iodine while efficient disinfection activity is maintained.In studies evaluating the efficacy of electrochemical disinfection methods to prevent biofilm formation and biofouling, workers have used a potential of approximately 1.0 V (12, 15, 16). A potential of 0.74 V versus a saturated calomel electrode applied to Saccharomyces cerevisiae resulted in decreased respiratory activity and cell death (12). This method has been FIG. 1. Time course of disinfection by potassium iodate and potassium periodate. Potassium iodate or potassium periodate (dissolved in 0.1 M phosphate buffer, pH 7.0) at concentrations of 0 mM (control), 0.1 mM, and 1.0 mM were incubated with an E. coli cell suspension (initial cell concentration; 1.0 ϫ 10 4 cells/ml).

No abstract