Akihiro Sakatoku

Acinetobacter sp. Ud-4 Efficiently Degrades Both Edible and Mineral Oils: Isolation and Characterization

A novel Acinetobacter strain, Ud-4, possessing a strong capacity to degrade edible, lubricating, and heavy oil was isolated from seawater in a fishing port located in Toyama, Japan. It was identified by morphological and physiological analyses and 16S rDNA sequencing. This strain could utilize five types of edible oils (canola oil, olive oil, sesame oil, soybean oil, and lard), lubricating oil, and C-heavy oil as the sole carbon source for growth in M9 medium. The strain grew well and heavily degraded edible oils in Luria–Bertani medium during a 7-day culture at 25°C; it also degraded all kinds of oils in artificial seawater medium for marine bacteria. Furthermore, this strain was capable of degrading almost all C10–C25 n-alkanes in C-heavy oil during a 4-week culture. Oligonucleotide primers specific to two catabolic genes involved in the degradation of n-alkanes (Acinetobacter sp. alkM) and triglyceride (Acinetobacter sp. lipA) allowed amplification of these genes in strain Ud-4. To our knowledge, this is the first report on the isolation of a bacterium that can efficiently degrade both edible and mineral oils.

Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa)

The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos.

Isolation of a novel Saccharophagus species (Myt-1) capable of degrading a variety of seaweeds and polysaccharides.

A bacterial strain, Myt‐1, was isolated in Toyama Bay in Toyama Prefecture, Japan. Myt‐1 was capable of reducing the thalli of various seaweed species to single cell detritus particles. A 16S rDNA homology search revealed that the closest relative of Myt‐1 was Saccharophagus degradans 2–40 (CP000282; 100% similarity), which was first isolated in Chesapeake Bay in Virginia, USA. The Myt‐1 strain was capable of degrading more than 10 polysaccharides, almost all of which were also degraded by S. degradans 2–40. Analyses of alginase gene DNA sequence homology, DNA–DNA homology, and zymogram analysis of obtained polysaccharidases suggested that Myt‐1 was a new species of Saccharophagus. Thus, Myt‐1 is only the second species in this genus, which has contained only one strain and species since 1988, and was tentatively designated Saccharophagus sp. Myt‐1. Myt‐1 has considerable potential for reducing the volume of seaweed wastes, and for producing functional materials from seaweed substrate.

Induction of deflagellation by various local anesthetics in Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae)

Dibucaine, a local anesthetic, is known to induce flagellar excision in Chlamydomonas reinhardtii. Herein, we investigate whether other local anesthetics have similar effects. Tetracaine, bupivacaine, procaine, and lidocaine also caused flagellar excision, although their potencies were lower than that of dibucaine. Bupivacaine, procaine, and lidocaine induced a morphological change in flagella from a rod‐like shape to a disk‐like shape before flagellar excision. Except for lidocaine, these local anesthetics caused cell‐wall shedding in addition to flagellar excision. The anesthetics in order of their median effective concentration (1‐h EC50) for flagellar excision are as follows: dibucaine (1.37 × 10−5 M) < tetracaine (3.16 × 10−5 M) < bupivacaine (4.25 × 10−4 M) <  procaine (2.02 × 10−3 M) < lidocaine (3.61 × 10−3 M). In all cases, Ca2+ depletion from the solution inhibited flagellar excision. However, Ca2+‐channel blockers, IP3 receptor antagonists, and inhibitors of phospholipase C did not prevent excision. We suggest that the local anesthetics induce flagellar excision by increasing the fluidity of the flagellar/cell membrane, thereby allowing extracellular Ca2+ to flow into the cell and cause flagellar excision.

Discovery and biogeochemistry of asphalt seeps in the North São Paulo Plateau, Brazilian Margin

An initial multiple biogeochemical dataset was acquired from the first discovered asphalt seeps in the Brazil margin during deep-sea dive surveys in 2013 using a manned submersible. These surveys were conducted on the outer escarpment of the North São Paulo Plateau. Sediment cores taken from the submersible were processed for pore water and sediment biogeochemistry. The silica concentration, as a chemical geothermometer, showed a steep gradient in the pore water, which indicates the possibility of an active brine system operating in the seepage area. Rare earth elements were used as powerful tracers of chemical processes. Low rare earth element concentrations in both asphalt and Fe-Mn oxyhydroxide-phase sediments suggests that rare earth elements were released during the oil fractionation and biodegradation processes and further depleted under the reducing environment. The main bacterial communities of the sediment were Proteobacteria in the asphalt sites, while at non-asphalt sites, the main bacterial communities of sediment were Firmicutes. Stable carbon and nitrogen isotopes were used to determine the food sources of the heterotrophs, and results suggest that asphalt probably provides a carbon source for these benthic animals. This study may provide useful information to clarify the impact of heavy hydrocarbon seepage on the marine ecosystem.

Seasonal variations in bacterioplankton community structures in two small rivers in the Himi region of central Japan and their relationships with environmental factors

The aim of this study was to improve our understanding of seasonal variations and the effects of physicochemical conditions on the bacterioplankton communities in two small rivers, the Moo and Nakayachi Rivers in the Himi region of central Japan. These rivers are inhabited by unionid freshwater mussels, which are used for oviposition by the endangered Itasenpara bitterling (Acheilognathus longipinnis). Water samples were collected every month between March 2011 and February 2012. Changes in bacterioplankton community structures were analysed using an approach that did not require cultivating the bacteria and involved PCR and denaturing gradient gel electrophoresis. The bacterioplankton community structures in the two rivers were similar in all seasons except winter. The bacterial sequences identified were dominated by typical freshwater Actinobacteria, Bacteroidetes, Cyanobacteria, α-Proteobacteria, and β-Proteobacteria bacterioplankton. Many β-Proteobacteria species were detected in all seasons, but Bacteroidetes species were dominant in the winter. The bacterioplankton community structures were affected by biochemical oxygen demand, chemical oxygen demand, chlorophyll-a concentration, water depth, and water temperature. These results provide a foundation for a more detailed understanding of the conditions that provide a suitable unionid habitat.