Protistan grazing and viral lysis losses of bacterial carbon production in a large mesotrophic lake (Lake Biwa)

Published online: 18 April 2014The grazing and lysis mortalities of planktonic bacteria were estimated using the modified dilution method and respiratory quinone (RQ) analysis in mesotrophic Lake Biwa, Japan. The planktonic bacterial assemblages in the lake consisted of various RQ subgroups with different growth and mortality rates. The sum of total bacterial mortalities due to protistan grazing and viral lysis accounted for 96.6 % (range 89.0–107.2 %) of daily total bacterial production. This is the first report that successfully demonstrates a balanced relationship between bacterial production and losses using the modified dilution method in a lake. The growth rates of ubiquinone (UQ)-containing bacteria were faster than those of menaquinone-containing bacteria. Especially the dominant and fastest growing bacterial groups in the present study were the bacterial groups containing UQ-8 or UQ-10. The sum of their production and loss accounted for 60 % of carbon fluxes within the microbial loop. Thus, a large portion of the carbon cycling through the bacterial community in Lake Biwa can be explained by the carbon fluxes through dominant bacterial groups

A Face-like Structure Detection on Planet and Satellite Surfaces using Image Processing

This paper demonstrates that face-like structures are everywhere, and can be de-tected automatically even with computers. Huge amount of satellite images of the Earth, the Moon, the Mars are explored and many interesting face-like structure are detected. Throughout this fact, we believe that science and technologies can alert people not to easily become an occultist.Comment: 4 page

Influence of River Inflow and Microbial Activity on Distribution of Dissolved Organic Carbon in the Northern Part of Ariake Sea, Kyushu, Japan

To identify the factors controlling the distribution of dissolved organic carbon (DOC) in the northern Ariake Sea (Japan), we measured DOC, salinity and chlorophyll a (Chl. a) along transect lines from the largest river discharging into the Ariake Sea (the Chikugo River) to the opposite shore. The DOC concentration was significantly correlated with salinity, although no correlation was found between the Chl. a concentration and DOC. Thus, river inflow is the primary source of DOC. However, the expected concentration of riverine DOC, represented by the y-intercept of the regression curve between salinity and DOC, was much higher than the DOC concentration of the Chikugo River, suggesting the presence of additional DOC sources to the Ariake Sea. We conducted particulate organic matter (POM) decomposition experiments and observed DOC production after incubation. Thus, microbial POM decomposition may be a source of excess DOC. This study is the first to show that river inflow and microbial decomposition of POM affect the DOC distribution in the northern Ariake Sea

Spatio-temporal distribution of environmental DNA derived from Japanese sea nettle jellyfish Chrysaora pacifica in Omura Bay, Kyushu, Japan

We surveyed the spatial and temporal distribution of Japanese sea nettle jellyfish Chrysaora pacifica in Omura Bay, Japan, using an environmental DNA (eDNA) method. In 2018, the C. pacifica eDNA concentration increased from March?May at all depths. The seasonal pattern of C. pacifica eDNA was consistent with previous reports based on visual observations along the Japanese coast. Thus, the eDNA method might have advantages to follow the seasonal pattern of C. pacifica while being less time-consuming and less laborious compared with traditional methods. The eDNA concentrations tended to reach a maximum near and/or below the pycnocline throughout this study. Therefore, the vertical distribution of C. pacifica medusae may have been restricted by strong pycnocline formation in July and August 2018. However, even with a weak pycnocline, which C. pacifica should be able to swim across, the apparent distribution of C. pacifica eDNA seems to be restricted by the pycnocline. Therefore, the eDNA method cannot, currently, accurately assess the absolute vertical distribution pattern of C. pacifica, especially when a pycnocline is formed

琵琶湖における異なる呼吸鎖キノンを保持する細菌亜集団の増殖と死滅

京都大学0048新制・課程博士博士(理学)甲第17775号理博第3898号新制||理||1562(附属図書館)30582京都大学大学院理学研究科生物科学専攻(主査)教授 中野 伸一, 准教授 奥田 昇, 教授 疋田 努学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDGA

Estimation of carbon biomass and community structure of planktonic bacteria in Lake Biwa using respiratory quinone analysis

Published online: 19 February 2013The relationship between bacterial respiratory quinone (RQ) concentration and biomass was assessed for Lake Biwa bacterial assemblages to evaluate the utility of bacterial RQ concentration as an indicator of bacterial carbon. The biomass estimated from the RQ concentration correlated well with that from cell volume, indicating that RQ concentration is an appropriate indicator of bacterial biomass. The estimated carbon content per unit of RQ (carbon conversion factor) of bacteria was 0.67 mg C nmol RQ−1. Bacterial carbon biomass, which was estimated from the RQ concentration using the conversion factor, ranged between 0.008 and 0.054 mg C L[−1] (average 0.025 mg C L[−1]) at 5 m depth and between 0.010 and 0.024 mg C L[−1] (average 0.015 mg C L[−1]) at 70 m depth. Ubiquinone-8-containing bacteria dominated the epilimnion and hypolimnion. Compared to conventional image analysis, bacterial RQ analysis is a less laborious method of simultaneously determining bacterial biomass and community

High contribution of Synechococcus to phytoplankton biomass in the aphotic hypolimnion in a deep freshwater lake (Lake Biwa, Japan)

The effective transportation of picophytoplankton to the mesopelagic layer in the ocean by cell aggregation and attachment to large particles has been reported. Those findings suggest that picophytoplankton play important roles in ecological processes in the deep ocean. However, there is no information about vertical transportation of picophytoplankton cells from the epilimnion in lakes, though the presence of picophytoplankton cells in the hypolimnion has been reported. The present study demonstrated the possible importance of Synechococcus (Cyanobacteria) in ecological processes of the hypolimnion in the deep mesotrophic Lake Biwa, Japan. The chlorophyll a concentration in the 0.2-2.0-µm fraction, which is mainly derived from Synechococcus, accounted for a large portion (up to 28.8%) of the total chlorophyll a concentration in the hypolimnion during the thermal stratification period. We found a significant positive correlation between Synechococcus abundances in the epilimnion and hypolimnion during the stratification period. In addition, our incubation experiment revealed that Synechococcus did not show significant growth during the first 2 d in dark conditions. These results suggest the recent delivery of a significant fraction of Synechococcus cells from the epilimnion to the hypolimnion. Our results indicate that the abundance of Synechococcus makes a greater contribution to ecological processes in the hypolimnion of Lake Biwa than previously hypothesized, and this may also be the case for other deep lakes

High-throughput sequencing shows inconsistent results with a microscope-based analysis of the soil prokaryotic community

In the present study, we perform the first direct analysis on how the composition of the prokaryotic soil community differs depending on whether high-throughput sequencing or fluorescent in situ hybridization (FISH) coupled with catalyzed reporter deposition (CARD) is used. Soil samples were collected along short (<3 m) tundra vegetation gradients from Northern Sweden. Relative abundances of Acidobacteria and Bacteroidetes estimated by the high-throughput sequencing were higher than those estimated by CARD–FISH, while relative abundances of Archaea and α-Proteobacteria estimated by high-throughput sequencing were lower than those estimated by CARD–FISH. The results indicated that the high-throughput sequencing overestimates/underestimates the relative abundance of some microbial taxa if we assume that CARD–FISH can provide potentially more quantitative data. Great caution should be taken when interpreting data generated by molecular technologies (both of high-throughput sequencing and CARD–FISH), and supports by multiple approaches are necessary to make a robust conclusion

Dissolved and Particulate Organic Matter Dynamics Relative to Sediment Resuspension Induced by the Tidal Cycle in Macrotidal Estuaries, Kyushu, Japan

The tide-induced resuspension of sediments plays important roles in the efflux of particulate organic carbon (POC) from rivers to the coastal sea. Although dissolved organic carbon (DOC) comprises more than half of the riverine flux of organic carbon to the ocean, the influence of sediment resuspension induced by the tidal cycle on DOC dynamics is largely unknown. This study examined the dynamics of POC, particulate organic nitrogen (PON), DOC, humic-like and protein-like fluorescent dissolved organic matter (DOM) in relation to the tidal cycle in the Chikugo and Hayatsue River Estuaries, Kyushu, Japan. This study is the first to show both the particulate organic matter (POM) and DOM dynamics in relation to the tidal cycle in the macrotidal estuaries. We found that the turbidity changed with the tidal cycle and that there were significant positive correlations of turbidity with POC and PON in the Chikugo River mouth, suggesting that tide-induced sediment resuspension supplied POM to the water column. The DOC concentration, humic-like and protein-like fluorescent DOM were not correlated with turbidity but were negatively correlated with salinity. These results suggest that POM efflux, but not DOM efflux, can be accelerated by tide-induced sediment resuspension in the macrotidal estuaries