Genetic and phenotypic studies on the strains biochemically identified as Shewanella putrefaciens, which had a G+C content ranging from 52 to 54 mol% were conducted. The moles percent G+C of the type strain of S. putrefaciens is 46. Surprisingly, DNA homology experiments revealed that all these strains are genetically related to Shewanella d g a (which was reported to produce tetrodotoxin), not to the type strain of S. putrefaciens. In this study, we reidentified clinical strains of S. putrefaciens which have a high range of moles percent G+C, as does S. alga. We also characterized the reidentified strains and found that the original description of S. alga (U. Simidu, K. Kita-Tsukamoto, T. Yasumoto, and M. Yotsu, Int. J. Syst. Bacteriol. 4k331-336, 1990) is insufficient to identify this strain. An emended description of S. alga is given.The organism now called Shewanella putrefaciens was first described in 1931 and classified as a member of the genus Achromobacter (4). In 1941, it was transferred to the genus Pseudomonas (16) on the basis of morphology. In 1972, it was transferred to the genus Alteromonas (1) on the basis of G+C content. Finally, in 1985, it was transferred to a new genus, Shewanella, on the basis of comparative 5s rRNA sequences (17). The type species of Shewanella is S. putrefaciens (17).Many of the strains classified as S. putrefaciens were isolated from diverse sources, including environmental sources, such as spoilage flora of foods (12, 14, 18,28), oil fields (24), and the ocean (1, 13), and diverse clinical sources, such as patients with otitis, bronchitis, pneumonia, and urinary tract infections (3, 6, 9, 14, 15, 21, 22,29). However, the collected strains were heterogeneous and there were differences between environmental and clinical isolates (9,14,20,21,23,24,28). Owen et al. (20) divided the 10 environmental strains and 16 clinical strains into four groups. Group IV consisted of nine clinical strains. The moles percent G+C value for group IV (52.6) was clearly higher than those for the other three groups (43.9 to 46.9). All four groups retained the species identification of S. putrefaciens, despite the obvious heterogeneity and moles percent G+C values ranging from 43 to 55 (2).Recently, we noticed that most strains isolated from human clinical specimens and identified as S. putrefaciens showed beta-hemolysis on sheep blood agar. However, environmental strains were nonhemolytic. These hemolytic strains had 52 to 54 mol% G+C. Although the hemolytic strains are biochemically identified as S. putrefaciens according to the description in the Manual of Clinical Microbiology (7), they exhibited high levels of DNA homology with the type strain of S. alga. In this study, we present evidence that these clinical strains of S. putrefaciens should be identified as S. alga and emend the description of S. alga * Corresponding author. S. alga is known to be a tetrodotoxin (lTX)-producing bacterium (25,26). Production of TTX by some newly reidentified strains was examined. This is the first report o...

SUMMARYTobacco cells (Nicotiana tabacum L.) accumulate harmful naphthols in the form of malonylated glucosides (Taguchi et al., 2005). Here, we showed that the malonylation of glucosides is a system to metabolize xenobiotics and is common to higher plants. Moreover, some plantlets including Arabidopsis thaliana excreted some of the incorporated naphthols into the culture media as their glucosides. In order to analyze the function of malonylation in the metabolism of these xenobiotics, we identified a malonyltransferase gene (At5g39050) responsible for the malonylation of these compounds in A. thaliana. The recombinant enzyme had malonyltransferase activity toward several phenolic glucosides including naphthol glucosides. A knockout mutant of At5g39050 (pmat1) exposed to naphthols accumulated only a few malonylglucosides in the cell, and released larger amounts of simple glucosides into the culture medium. In contrast, forced expression of At5g39050 in the pmat1 mutant resulted in increased malonylglucoside accumulation and decreased glucoside excretion to the media. The results provided clear evidence of whether the release of glucosides or the storage of malonylglucosides was determined by the At5g39050 expression level. A similar event in naphthol metabolism was observed in the tobacco mutant with a suppressed malonyltransferase gene (NtMaT1). These results suggested that malonylation could be a key reaction to separate the way of xenobiotics disposition, that is, release from cell surface or storage in vacuoles.

We characterized the pcb2 (pale-green and chlorophyll b reduced 2) mutant. We found through electron microscopic observation that chloroplasts of pcb2 mesophyll cells lacked distinctive grana stacks. High-performance liquid chromatography (HPLC) analysis showed that the pcb2 mutant accumulated divinyl chlorophylls, and the relative amount of divinyl chlorophyll b was remarkably less than that of divinyl chlorophyll a. The responsible gene was mapped in an area of 190 kb length at the upper arm of the 5th chromosome, and comparison of DNA sequences revealed a single nucleotide substitution causing a nonsense mutation in At5g18660. Complementation analysis confirmed that the wild-type of this gene suppressed the phenotypes of the mutation. Antisense transformants of the gene also accumulated divinyl chlorophylls. The genes homologous to At5g18660 are conserved in a broad range of species in the plant kingdom, and have similarity to reductases. Our results suggest that the PCB2 product is divinyl protochlorophyllide 8-vinyl reductase.

Structural variation in the stroma-grana (SG) arrangement of the thylakoid membranes, such as changes in the thickness of the grana stacks and in the ratio between grana and inter-grana thylakoid, is often observed. Broadly, such alterations are considered acclimation to changes in growth and the environment. However, the relation of thylakoid morphology to plant growth and photosynthesis remains obscure. Here, we report changes in the thylakoid during leaf development under a fixed light condition. Histological studies on the chloroplasts of fresh green Arabidopsis leaves have shown that characteristically shaped thylakoid membranes lacking the inter-grana region, referred to hereafter as isolated-grana (IG), occurred adjacent to highly ordered, large grana layers. This morphology was restored to conventional SG thylakoid membranes with the removal of bolting stems from reproductive plants. Statistical analysis showed a negative correlation between the incidences of IG-type chloroplasts in mesophyll cells and the rates of leaf growth. Fluorescence parameters calculated from pulse-amplitude modulated fluorometry measurements and CO assimilation data showed that the IG thylakoids had a photosynthetic ability that was equivalent to that of the SG thylakoids under moderate light. However, clear differences were observed in the chlorophyll a/b ratio. The IG thylakoids were apparently an acclimated phenotype to the internal condition of source leaves. The idea is supported by the fact that the life span of the IG thylakoids increased significantly in the later developing leaves. In conclusion, the heterogeneous state of thylakoid membranes is likely important in maintaining photosynthesis during the reproductive phase of growth.

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