Occurrence of domoic acid in tropical bivalves

Domoic acid was found in bivalves belonging to the genus Spondylus collected randomly from the Philippines, Vietnam, Thailand and Ishigaki Island, Japan. This is the first report of domoic acid accumulating in bivalves from tropical waters. Large differences in domoic acid levels were observed among the Spondylus specimens collected from different areas. The Spondylus specimens from the Philippines and Vietnam showed higher levels of domoic acid whereas the level in Spondylus spp. from Thailand and Japan was low. The highest level of domoic acid—more than four times the safe consumption level of 20 μg/g whole tissue—was found in a specimen from the Philippines. On the other hand, bivalves other than Spondylus collected from the same area at the same time in the Philippines showed very low levels of domoic acid, showing that bivalves belonging to the genus Spondylus accumulate specifically high levels of domoic acid. These results suggest the wide distribution of causative phytoplankton in tropical waters.     

Colonization and growth promotion characteristics of Enterobacter sp. and Herbaspirillum sp. on Brassica oleracea

We investigated the effects of inoculating a dicot plant, Brassica oleracea , with nitrogen-fixing endophytic bacteria isolated from monocots. The bacteria used were Enterobacter sp. strain 35 isolated from sugarcane and Herbaspirillum sp. strain B501 isolated from wild rice. Under glasshouse conditions, B. oleracea inoculated with strain 35 had a significantly greater fresh weight than uninoculated plants, and the fresh weight of plants inoculated with strain B501 tended to be higher than that of uninoculated plants. We conducted a laboratory-scale experiment to confirm the above results and to investigate the colonization and nitrogen-fixing abilities of these bacteria. Plants inoculated with Enterobacter sp. strain 35-1, a green fluorescent protein (GFP)-labeled strain derived from strain 35, had larger bacterial populations and greater acetylene reduction activity than those inoculated with Herbaspirillum sp. strain B501 gfp 1. Strain 35-1 colonized the intercellular spaces and the junctions of the lateral roots with the parent root. The results indicated that isolates from monocots can successfully colonize B. oleracea (a dicot) and promote plant growth.     

Occurrence of blood disease of banana in Sumatra,Indonesia

Since 1991, the sudden death of cultivated banana plants has been widely observed in the southern region of Sumatra Island, Indonesia. Wilting from loss of petiole and midrib turgidity, yellowing, and necrosis of leaves was followed by death of the whole plant. Reddish brown bacterial ooze exuded from the cut surface of infected pseudostems and fruits. The colony appearance of the isolated bacterium was similar to that of Ralstonia solanacearum. The bacterium was pathogenic to banana plants but not to tomato. Its bacteriological properties agreed with those of blood disease bacterium (BDB) of banana described previously. The 16S rDNA sequence of strain Banana E had conserved bases characteristic of BDB. Based on these results, the causal agent was identified as BDB, which is a close relative of Ralstonia. The isolates have resistance against antibiotics, such as chloramphenicol and tetracycline.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB095535     

The hrpZ and hrpA genes are variable, and useful for grouping Pseudomonas syringae bacteria

The hrpS to hrpB regions from strains of Pseudomonas syringae were amplified by polymerase chain reaction (PCR) and the DNA sequence determined. The order of hrpS, hrpA, hrpZ, and hrpB was consistent among P. syringae strains. The sequence of hrpS was highly conserved. In a cluster analysis with the hrpS sequence, P. syringae strains were divided into four groups (I, II, III, and IV) and one undetermined strain, in agreement with previous studies. In contrast, the hrpZ sequences contained insertions, deletions, and base substitutions followed by changes in amino acids. Based on cluster analysis of hrpA, hrpZ, and hrpB, P. syringae strains could be divided into five groups. One of the four groups (group I) in the cluster analysis of hrpS could be further divided into two subgroups (groups IA and IB). Groups II, III, and IV were the same in the two analyses. Group-specific primers were designed, based on the DNA sequences of hrpZ, that could differentiate the groups of P. syringae strains. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB112552 to AB112581