High level of calcium carbonate precipitation achieved by mixed culture containing ureolytic and nonureolytic bacterial strains.

This study demonstrates a remarkably high level of microbial-induced calcium carbonate precipitation (MICP) using a mixed culture containing TBRC 1396 (Priestia megaterium), TBRC 8147 (Neobacillus drentensis) and ATCC 11859 (Sporosarcina pasteurii) bacterial strains. The mixed culture produced CaCO3 weights 1·4 times higher than those obtained from S. pasteurii, the gold standard for efficient MICP processes. The three strains were selected after characterization of various Bacillus spp. and related species for their ability to induce the MICP process, especially in an alkaline and high-temperature environment. Results showed that the TBRC 1396 and TBRC 8147 strains, as well as TBRC 5949 (Bacillus subtilis) and TBRC 8986 (Priestia aryabhattai) strains, could generate calcium carbonate at pH 9-12 and temperature 30-40°C, which is suitable for construction and consolidation purposes. The TBRC 8147 strain also exhibited CaCO3 precipitation at 45°C. The TBRC 8986 and TBRC 8147 strains are nonureolytic bacteria capable of MICP in the absence of urea, which can be used to avoid the generation of undesirable ammonia associated with the ureolytic MICP process. These findings facilitate the successful use of MICP as a sustainable and environmentally friendly technology for the development of various materials, including self-healing concrete and soil consolidation.

An efficient purification and fractionation of genomic DNA from soil by modified troughing method.

AIMS: The aim of this study was to utilize a modified troughing method for purification of large genomic DNA obtained from microbiota in natural environment and for fractionation of genomic DNA into many size ranges that facilitates construction of metagenomic library. METHODS AND RESULTS: Genomic DNA extracted from soil or termite gut was purified by the modified troughing method which utilized gel electrophoresis in the presence of 30% PEG8000. The method performed better than various purification kits and allowed no significant loss in the amount of DNA recovered. In addition, the efficiency of the modified troughing method for DNA size fractionation was investigated. DNA size fractionation was achieved with repetitive rounds of electrophoresis and DNA collection to obtain DNA with many size ranges. CONCLUSIONS: The modified troughing method is a simple and efficient method for purification of genomic DNA and for DNA size fractionation. SIGNIFICANCE AND IMPACT OF THE STUDY: The modified troughing method is a straightforward and inexpensive technique readily available for anyone working with environmental genomic DNA. It facilitates cloning of genomic DNA and enhances rapid discovery of useful bioactive compounds from microbial resources.

Composition and functional characterization of yeast 66S ribosome assembly intermediates.

The pathway and complete collection of factors that orchestrate ribosome assembly are not clear. To address these problems, we affinity purified yeast preribosomal particles containing the nucleolar protein Nop7p and developed means to separate their components. Nop7p is associated primarily with 66S preribosomes containing either 27SB or 25.5S plus 7S pre-rRNAs. Copurifying proteins identified by mass spectrometry include ribosomal proteins, nonribosomal proteins previously implicated in 60S ribosome biogenesis, and proteins not known to be involved in ribosome production. Analysis of strains mutant for eight of these proteins not previously implicated in ribosome biogenesis showed that they do participate in this pathway. These results demonstrate that proteomic approaches in concert with genetic tools provide powerful means to purify and characterize ribosome assembly intermediates.

Correlation of two bioadhesion assays: the everted sac technique and the CAHN microbalance.

This contribution correlates two in vitro methods utilized to determine bioadhesion. One method, the everted intestinal sac technique, is a passive test for bioadhesion involving several polymer microspheres and a section of everted intestinal tissue. The other method, the CAHN microbalance, employs a CAHN dynamic contact angle analyzer with modified software to record the tensile forces measured as a single polymer microsphere is pulled from intestinal tissue. This study demonstrates that CAHN and everted sac experiments yield similar results when used to quantify the bioadhesive nature of polymer microsphere systems. A polymer showing high adhesion in one method also demonstrates high bioadhesion in the other method; polymers that exhibit high fracture strength and tensile work measurements with the CAHN microbalance also yield high binding percentages with the everted sac method. The polymers tested and reported here are poly(caprolactone) and different copolymer ratios of poly(fumaric-co-sebacic anhydride). The results of this correlation demonstrate that each method alone is a valuable indicator of bioadhesion.