Bacillus cereus from the environment is genetically related to the highly pathogenic B. cereus in Zambia

To follow-up anthrax in Zambia since the outbreak in 2011, we have collected samples from the environment and the carcasses of anthrax-suspected animals, and have tried to isolate Bacillus anthracis. In the process of identification of B. anthracis, we collected two isolates, of which colonies were similar to B. anthracis; however, from the results of identification using the molecular-based methods, two isolates were genetically related to the highly pathogenic B. cereus, of which clinical manifestation is severe and fatal (e.g., pneumonia). In this study, we showed the existence of bacteria suspected to be highly pathogenic B. cereus in Zambia, indicating the possibility of an outbreak caused by highly pathogenic B. cereus.     

Heat shock decreases the embryonic quality of frozen-thawed bovine blastocysts produced in vitro

In this study, the effect of heat shock on frozen-thawed blastocysts was evaluated using in vitro-produced (IVP) bovine embryos. In experiment 1, the effects of 6 h of heat shock at 41.0 C on fresh blastocysts were evaluated. HSPA1A expression as a reflection of stress was increased by heat shock (P < 0.05), but the expressions of the quality markers IFNT and POU5F1 were not affected. In experiment 2, frozen-thawed blastocysts were incubated at 38.5 C for 6 h (cryo-con) or exposed to heat shock at 41.0 C for 6 h (cryo-HS). Then, blastocysts were cultured at 38.5 C until 48 h after thawing (both conditions). Cryo-HS blastocysts exhibited a decreased recovery rate: HSPA1A expression was dramatically increased compared with that in fresh or cryo-con blastocysts at 6 h, and IFNT expression was decreased compared with that in cryo-con blastocysts at 6 h (both P < 0.05). Cryo-con blastocysts at 6 h also exhibited higher HSPA1A expression than fresh blastocysts (P < 0.05). At 48 h after thawing, the number of hatched blastocysts and blastocyst diameter were lower in cryo-HS blastocysts (P < 0.05). Cryo-con blastocysts showed lower POU5F1 levels at 48 h than fresh, cryo-con or cryo-HS blastocysts at 6 h (P < 0.05), but their POU5F1 levels were not different from those of cryo-HS blastocysts at 48 h. These results indicated that application of heat shock to frozen-thawed blastocysts was highly damaging. The increase in damage by the interaction of freezing-thawing and heat shock might be one reason for the low conception rate in frozen-thawed embryo transfer in summer.     

High water-temperature tolerance in photosynthetic activity of <Emphasis Type="Italic">Zostera marina</Emphasis> seedlings from Ise Bay,Mie Prefecture,central Japan

Photosynthetic activities of seedlings of Zostera marina were successively measured using a gas volumeter for 6 days at seven light (0–400 μmol photons/m² per s) and 11 water temperature conditions (5–35°C). The seedlings were collected from mature plants (Ise Bay, central Japan), and stored and cultured in incubators accurately controlled at each test temperature. The maximum gross photosynthesis (P _maxg) was recorded at an optimal water temperature of 29°C after 0 days. After 6 days, P _maxg appeared at 25°C and most plants cultured at 29–30°C bleached and withered after the drastic increase of light compensation point (I _c). On the contrary, at 5–28°C, the photosynthetic activities either changed little (5–25°C) or recovered after a temporal reduction (26–28°C); seedlings survived and looked healthy after being cultured for 6 days. The recovery was thought to be an acclimation to tolerate higher water temperature. As a result, the critical upper water temperature for Z. marina seedlings was proposed as 28°C. The temperature was consistent with the previously reported maximum water temperature in habitats around the southern boundary of Z. marina in the northern hemisphere.     

Relationships between critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum

SUMMARY: This study was designed to determine the critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum . Sampling and measurement of natural light conditions were carried out in the S. macrocarpum population at a depth of 8 m off Kiwado in Fukawa Bay, Yamaguchi Prefecture, Japan, from April to June 1998. Photosynthesis and respiration of the juvenile thalli, and diurnal changes in solar irradiance were measured for the same period. The critical photon irradiance for growth of the juvenile thalli observed on the population floor was 1.0–1.5% on the sea surface. The photosynthetic rate of leaf of juvenile thalli increased linearly with increasing photon irradiance when light levels were lower than 50 μM/m² per s. The respiratory rate and light compensation point of the juvenile thalli were 2.49 μL O₂/cm² per h and 4.98 μM/m² per s, respectively. The daily compensation point was estimated with a mathematical model based on photosynthesis–light equations and diurnal changes in solar irradiance. For a day of average solar irradiance over the period of the present study, the estimated daily compensation point of the juvenile thalli was 1.3% on the sea surface. This value agreed well with the observed critical photon irradiance for growth of juvenile S . macrocarpum on the population floor. The results of the study confirm that the mathematical model is effective for estimating the daily compensation point.     

Determination of the geographic origin of rice by chemometrics with strontium and lead isotope ratios and multielement concentrations

The objective of this study was to develop a technique for determining the country of origin of rice in the Japanese market. The rice samples included a total of 350 products grown in Japan (n = 200), the United States (n = 50), China (n = 50), and Thailand (n = 50). In this study, (87)Sr/(86)Sr and Pb isotope ((204)Pb, (206)Pb, (207)Pb, and (208)Pb) ratios and multielement concentrations (Al, Fe, Co, Ni, Cu, Rb, Sr, and Ba) were determined by high-resolution inductively coupled plasma mass spectrometry. By combining three chemometric techniques based on different principles and determination criteria, the countries of origin of rice were determined. The predictions made by 10-fold cross-validation were around 97% accurate. The presented method demonstrated the effectiveness of determining the geographic origin of an agricultural product by combining several chemometric techniques using heavy element isotope ratios and multielement concentrations.     

Positive correlation between the number of root nodule primordia and seed sugar secretion in soybean (Glycine max L.) seedlings inoculated with a low density of Bradyrhizobium japonicum

Sufficient rhizobium population in the rhizosphere of legume seedlings is required for early and enough setting of root nodules. Potential of seed and seedling root exudates for proliferation of Bradyrhizobium japonicum PNT119 was evaluated in the soybean cvs. Enrei and Tachinagaha. In both cultivars, seed exudates showed a higher potential than root exudates. In the seed exudates, a low-molecular high-polarity fraction including sugars and amino acids showed a higher potential than both high-molecular fraction and low-molecular low-polarity fraction. The correlations between the sugar or amino acid contents of seed exudates and the number of root nodule primordia at 7 d after sowing were investigated among 12 soybean cultivars. When seeds were inoculated with a low rhizobium density, a high correlation coefficient was detected between them. However, there was no positive correlation in the plants inoculated with a high rhizobium density. These results suggest that the amount of low molecular substances in the seed exudates determines the number of root nodule primordia through rhizobium proliferation around seed and young roots when the rhizobium density is the limiting factor. The genetic trait relating to seed coat secretion should be considered as a possible key factor contributing to adequate root nodulation in soybean seedlings cultivated in fields with a low rhizobium density.     

Genotyping‐by‐sequencing for construction of a new genetic linkage map and QTL analysis of growth‐related traits in Pacific bluefin tuna

Pacific bluefin tuna (Thunnus orientalis) has high market value, but its wild populations have decreased in recent years. The broodstock of Pacific bluefin tuna that were hatched artificially and reared under aquaculture conditions is beginning to be used for production. The creation of broodstock with commercially valuable traits, such as rapid growth, is therefore of great interest. Genetic linkage map‐based identification of markers associated with quantitative trait loci (QTLs) facilitates marker‐assisted selection (MAS) breeding and allows efficient genetic improvement of broodstock. Single nucleotide polymorphism (SNP)‐based genetic linkage map construction using the genotyping‐by‐sequencing method can expand the number of mapped markers and help identify growth‐related QTLs. In this study, we constructed sex‐specific maps for 24 linkage groups consisting of 677 SNP and 651 microsatellite markers. The total lengths of 93 progenies in the mapping population followed normal distribution, with an average length of 9.4 mm. We performed composite interval mapping in the mapping population. QTL analysis revealed one significant QTL in LG10 on the female linkage map. The genetic linkage map—the second such map generated for Pacific bluefin tuna—and the growth‐related QTLs detected in this study will be useful for tuna aquaculture MAS programs.     

High water temperature tolerance in photosynthetic activity of <Emphasis Type="Italic">Zostera japonica</Emphasis> Ascherson &; Graebner seedlings from Ago Bay,Mie Prefecture,central Japan

Photosynthetic activity of Zostera japonica seedlings was measured using a gas volumeter at 0 and 6 days in culture under eight light (0–800 μmol photons/m²/s) and ten water temperature conditions (5–35°C). Seedlings from Ago Bay, Mie Prefecture were cultured in incubators accurately controlled at each test temperature for 1 week. After 1 week, maximum gross photosynthesis (P _maxg) appeared at 29°C and most seedlings cultured at 30–35°C bleached and withered. At the same time, the light compensation point (I _c) increased only at 30°C during the culture period. As a result, the upper critical water temperature for survival was 29°C in Z. japonica seedlings, which agrees well with that for the southern boundary of Z. japonica around Japanese coast. It is necessary to monitor this species around this boundary as a bio-indicator for seawater warming.