The effects of inundation caused by the 2011 Tohoku tsunami on soil bacterial communities in agricultural fields were evaluated. Bacterial communities were compared across three different types of soil, unflooded field (UF) soil, soil flooded for 2 weeks (short term (ST)), and soil flooded for 2 months (long term (LT)), using polymerase chain reaction-pyrosequencing of 16S rRNA genes. Acidobacteria were dominant in UF, with a relative abundance of approximately 35 %, and Proteobacteria dominated flooded soils (30-67 %). Hierarchical cluster analysis indicated that the community structure of soil bacteria in flooded soils (ST and LT) clearly differed from that in UF. Differences between LT and ST fields were rarely observed in terms of chemical properties and microbial community structure at the phylum level. However, sulfur-oxidizing bacteria (SOB) and nitrite-oxidizing bacteria (NOB) in LT tended to occur at high and low abundances, respectively. Halothiobacillus, a halotolerant SOB, was detected in all LT fields. Unexpectedly, a zeta-Proteobacteria, which had previously only been detected in marine environments, was detected in LT fields only. Our results demonstrate that the effects of the 2011 Tohoku tsunami on soil bacterial communities in agricultural fields may have lasted at least 1 year. Furthermore, SOB, NOB, and zeta-Proteobacteria may serve as indicators of the effects of seawater inundation on microorganisms.

Since the growth promoter effect of antibiotics was found, many kinds of antibiotics have been used as feed additives for the improvement of growth performance. Since January 1, 2006, however, European Parliament prohibited the use of antibiotics as feed additives for promoting animal growth because of biosecurity threats arising from the increasing resistance of pathogens to antibiotics. Thereafter, various natural substrates having the growth promoter effect have been attempted to use as feed additives instead of antibiotics. Honeybees collect propolis from the cracks in the bark of trees, and it has the versatile pharmacological activities including antibacterial effect. Therefore, the present study aimed to examine the influence of propolis residue, which was the residue after ethanol extraction, on the cecal bacterial flora in the meat-type chicken, Nanbu Kashiwa. Twenty-eight-d-old female Nanbu Kashiwa were given an ordinary diet for 90 days. During last 10 days, an experimental diet including 2% of propolis residue was provided. At the end of experimental period, ceca were removed and DNA was isolated from cecal content. The V3 region of the bacterial 16S rRNA gene was amplified by PCR using the 357F-GC and 518R primers. To indentify the bacterial diversity, denaturing gradient gel electrophoresis (DGGE) was applied, and the optical intensity of DGGE bands was determined. The major bands were excised, and DNA was reamplified by PCR. The sequencing data were analyzed by the Basic Local Alignment Search Tool (BLAST) of DNA Data Bank of Japan. The bacteria identified by PCR-DGGE and BLAST were Lactobacillus aviaries, Lactobacillus, Olsenella, Coriobacterium, Paraprevotella, Prevotellaceae, Clostridiaceae and Bacteroidaceae. The DGGE band of which the optical intensity of the propolis residue group was lower than the control group was the family Prevotellaceae. The successful use of propolis residue to reduce the family Prevotellaceae showed the possibility to use propolis residue as alternative feed additives.

No abstract