Identification of a 4-Deoxy-l-erythro-5-hexoseulose Uronic Acid Reductase,FlRed, in an Alginolytic Bacterium Flavobacterium sp. Strain UMI-01

In alginate-assimilating bacteria, alginate is depolymerized to unsaturated monosaccharide by the actions of endolytic and exolytic alginate lyases (EC 4.2.2.3 and EC 4.2.2.11). The monosaccharide is non-enzymatically converted to 4-deoxy-l-erythro-5-hexoseulose uronic acid (DEH), then reduced to 2-keto-3-deoxy-d-gluconate (KDG) by a specific reductase, and metabolized through the Entner–Doudoroff pathway. Recently, the NADPH-dependent reductase A1-R that belongs to short-chain dehydrogenases/reductases (SDR) superfamily was identified as the DEH-reductase in Sphingomonas sp. A1. We have subsequently noticed that an SDR-like enzyme gene, flred, occurred in the genome of an alginolytic bacterium Flavobacterium sp. strain UMI-01. In the present study, we report on the deduced amino-acid sequence of flred and DEH-reducing activity of recombinant FlRed. The deduced amino-acid sequence of flred comprised 254 residues and showed 34% amino-acid identities to that of A1-R from Sphingomonas sp. A1 and 80%–88% to those of SDR-like enzymes from several alginolytic bacteria. Common sequence motifs of SDR-superfamily enzymes, e.g., the catalytic tetrad Asn-Lys-Tyr-Ser and the cofactor-binding sequence Thr-Gly-x-x-x-Gly-x-Gly in Rossmann fold, were completely conserved in FlRed. On the other hand, an Arg residue that determined the NADPH-specificity of Sphingomonas A1-R was replaced by Glu in FlRed. Thus, we investigated cofactor-preference of FlRed using a recombinant enzyme. As a result, the recombinant FlRed (recFlRed) was found to show high specificity to NADH. recFlRed exhibited practically no activity toward variety of aldehyde, ketone, keto ester, keto acid and aldose substrates except for DEH. On the basis of these results, we conclude that FlRed is the NADH-dependent DEH-specific SDR of Flavobacterium sp. strain UMI-01.     

Microbial reduction mechanism of ferric iron in paddy soils (Part I)

In the previous paper¹⁾ the authors proved that the ferric iron reduction in submerged paddy soils is entirely or mostly effected by the activities of microorganisms in the soil. Prior to the study on the ferric iron reducing microorganisms isolated from the soil, the present paper reports the research for the microbial mechanism of iron reduction. working with the soil itself.     

Effect of flutianil on the morphology and gene expression of powdery mildew

Flutianil, a fungicide effective only on powdery mildew, was previously reported to affect the host cell''s haustorial formation and nutrient absorption. Studies were conducted to investigate flutianil''s primary site of action on Blumeria graminis morphology using transmission electron microscope (TEM) observation and RNA sequencing (RAN-seq) techniques. TEM observation revealed that flutianil caused the extra-haustorial matrix and fungal cell wall to be obscured, without remarkable changes of other fungal organelles. RNA-seq analysis indicated that, unlike other powdery-mildew fungicides, flutianil did not significantly affect the constantly expressed genes for the survival of B. graminis. Genes whose expression is up- or downregulated by flutianil were found; these are the three sugar transporter genes and various effector genes, mainly expressed in haustoria. These findings indicate that the primary site of action of flutianil might be in the haustoria.     

Anatomical characterization of decayed wood in standing light red meranti and identification of the fungi isolated from the decayed area

To further our understanding of wood decay in living light red meranti (Shorea smithiana) trees, microscopic characteristics of the cell and cell wall degradations of S. smithiana wood in the presence of the decay fungi, the identity of the causal fungi, and the decay potential and pattern by an isolated fungus were investigated. Cell wall degradations, including cell wall thinning, bore holes formation, rounded pit erosion, and eroded channel opening were clearly observed under light and scanning electron microscopy. In transverse view, many large voids resulting from a coalition of degraded wood tissue appeared in the decayed canker zone. All these observations suggest the well-known simultaneous decay pattern caused by white-rot fungi. By phylogenetic analysis based on the sequences of internal transcribed spacer region of ribosomal DNA, a basidiomycete fungus isolated from the decayed wood was identified as Schizophyllum commune. The degradation caused by this fungus on sound S. smithiana wood in an in situ laboratory decay test was classified as the early stage of simultaneous decay, and showed a similar pattern to that observed in the wood samples naturally decayed.     

An index for evaluating the flood-prevention function of paddies

Urbanization is expanding in and around small to medium-sized cities as well as in large cities, and the expansion includes low-lying areas where the flood risk is high. Flood risk in small watersheds has been evaluated using precise mathematical models. However, these models cannot be applied to larger basins due to the complexity of data collection and analysis. As a result, quantitative evaluations of flood risk at macro scales and the flood-prevention function of paddies around urban areas have not been made. This paper proposes a method and an index that can be used to evaluate the flood-prevention function of paddies on a regional scale. In addition, the use of this system for basin-wide management is illustrated by an example for the Kinu and Kokai rivers, which are tributaries of the Tone River of Japan. The applicability of the approach is evaluated using data from a major flood that occurred in the study area.     

Ineffectiveness of pruning to control citrus huanglongbing caused by <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter americanus

The huanglongbing (HLB) disease of citrus trees, caused by Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, was first reported in Brazil in March, 2004. The presence of the disease has caused serious concerns among growers. Pruning experiments were conducted to determine if removal of symptomatic branches or the entire canopy (decapitation) would eliminate infected tissues and save HLB-affected trees. Pruning was done in five blocks on a total of 592 3- to 16 year-old ‘Valência’, ‘Hamlin’ or ‘Pêra’ sweet orange trees showing no symptoms or with two levels of symptom severity. Ten decapitated trees per block were caged and all trees were treated with insecticides to control the psyllid vector, Diaphorina citri. Mottled leaves reappeared on most symptomatic (69.2%) as well on some asymptomatic (7.6%) pruned trees, regardless of age, variety, and pruning procedure. Presence of the pathogen (Ca. Liberibacter americanus) in all symptomatic trees was confirmed by PCR. In general, the greater the symptom severity before pruning the lower the percentage of trees that remained asymptomatic after pruning.     

Seedborne fungi detected on stored solanaceous berry seeds and their biological activities

We isolated 629 fungi from 1296 berry seeds of solanaceous plants, including tomato (Lycopersicon esculentum), eggplant (Solanum melongena), bell pepper (Capsicum annuum), and red pepper (Capsicum annuum var. annuum) preserved for long and short terms. The isolates were classified into 22 genera excluding unidentified fungi, and the fungal floras were divided into two types: the tomato–eggplant and pepper groups. The results of cluster analysis with unweighted pair-group method with arithmetic average also supported these groups. Most tomato seeds infested with Geotrichum candidum germinated and grew the same as uninfested seeds. Cladosporium sphaerospermum and Arthrinium sp. isolated from eggplant seeds strongly suppressed germination, and Penicillium variabile suppressed seminal root elongation on eggplant. Alternaria alternata, Botrytis cinerea, and Myrothecium verrucaria detected from red pepper or bell pepper seeds were pathogenic to the fruits and the seedlings after artificial inoculation.     

Exposure to blue LED light before the onset of darkness under a long‐day photoperiod alters melatonin secretion,feeding behaviour and growth in female dairy calves

The effect of blue LED on melatonin secretion, feeding behaviour and growth was addressed in Holstein female dairy calves. In Exp.1, six animals (8 weeks old, 97 ± 4.1 kg BW) were exposed to yellow or blue LED for 2 hr before darkness over 7 days under a long‐day photoperiod (LDPP). In Exp. 2, six animals (8 weeks old, 88.5 ± 4.8 kg BW) were exposed to blue light from a white LED all daytime or a yellow LED for 2 hr before the darkness of LDPP (blue light cut) over 3 weeks. In Exp. 1, blue light mildly suppressed melatonin secretion during the 2‐hr treatment but did not affect the timing of the nightly melatonin rise. However, the rise in nighty melatonin levels was higher with yellow than blue LED. In Exp. 2, white LED completely suppressed melatonin secretion during the 2‐hr treatment, but plasma melatonin concentrations were similar during the darkness. Grass hay intake, rumination time, frequency of water intake and body weight gain were higher in animals exposed to the yellow rather than the white LED. Overall results indicate that exposure to blue light from white LEDs under an LDPP suppresses melatonin secretion and might negatively impact the development of female dairy calves.