The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors. During the meltdowns, a type of condensed particle, a caesium-rich micro-particle (CsMP), formed inside the reactors via unknown processes. Here we report the chemical and physical processes of CsMP formation inside the reactors during the meltdowns based on atomic-resolution electron microscopy of CsMPs discovered near the FDNPP. All of the CsMPs (with sizes of 2.0–3.4 μm) comprise SiO2 glass matrices and ~10-nm-sized Zn–Fe-oxide nanoparticles associated with a wide range of Cs concentrations (1.1–19 wt% Cs as Cs2O). Trace amounts of U are also associated with the Zn–Fe oxides. The nano-texture in the CsMPs records multiple reaction-process steps during meltdown in the severe FDNPP accident: Melted fuel (molten core)-concrete interactions (MCCIs), incorporating various airborne fission product nanoparticles, including CsOH and CsCl, proceeded via SiO2 condensation over aggregates of Zn-Fe oxide nanoparticles originating from the failure of the reactor pressure vessels. Still, CsMPs provide a mechanism by which volatile and low-volatility radionuclides such as U can reach the environment and should be considered in the migration model of Cs and radionuclides in the current environment surrounding the FDNPP.

The phylogenetic relationships of 50 reference strains, mostly marine bacteria which require Na+ for growth, were determined on the basis of 600 16s rRNA nucleotides by using reverse transcriptase sequencing. Strains belonging to 10 genera were included (four genera of the family Vibrionaceae, the genus Aeromonas of the family Aeromonaduceae, and the genera Alteromonas, Marinomonas, Shewanella, Pseudomonas, and Deleya). The sequences were aligned, the similarity values and evolutionary distance values were determined, and a phylogenetic tree was constructed by using the neighbor-joining method. On the basis of our results, the family Vibrionaceae was separated into at least seven groups (genera and families). Kbrio murinus clearly was on a line of descent that was remote from other vibrios. As determined by the similarity and evolutionary distance values, V. marinus is more distantly related to the family Vibrionaceae than the members of the Aeromonadaceae are. Also, Vibrio cholerae strains formed a separate group with Vibrio mimicus at the genus level. Of 30 species of the Vibrionaceae, 17 formed a large phylogenetic cluster. The genus Listonella was found to be a heterogeneous group, and the species were distributed in various subgroups of the Vibrionaceae. The separation of the family Aeromonadaceae from the family Vibrionaceae and the separation of the genera Marinomonas and Shewanella from the genus Alteromonas were confirmed in this phylogenetic study. However, a marine Pseudomonas species, Pseudomonas rtuutica, was clearly separated from two terrestrial Pseudomonas species. Each group that was separated by the phylogenetic analysis had characteristic 16s rRNA sequence patterns that were common only to species in that group. Therefore, the characteristic sequences described in this paper may be useful for identification purposes.Heterotrophic bacteria which are gram negative and motile by means of flagella are commonly isolated from marine environments and apparently are a major component of the bacterial flora of the sea. On the basis of their ability to ferment carbohydrates, these organisms can be divided into two groups. The fermentative strains have been assigned to the genera Vibrio, Listonella, Photobacterium, Colwellia (lo), and Aeromonas, and the nonfermentative strains have been included in the genera Alteromonas, Pseudomonas, Alcaligenes, Deleya, Marinomonas, Shewanella , and Flavobacterium (1).The family Hbrionaceae is one of the most important bacterial groups in marine environments. Members of this family often predominate in the bacterial flora of seawater, plankton, and fish. In a survey carried out in the West Pacific Ocean, vibrios accounted for nearly 80% of the bacterial population in surface seawater (31). Members of the Vibrionaceae are also the main organisms present in the intestinal flora of marine fish (30). In addition, some members of the Vibrionaceae are important pathogens for humans and animals.The marine members of the Kbrionaceae have been the subject of many taxonomic stud...

A 492-to 495-bp fragment of the gene coding for the large subunit of the form I ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) (rbcL) was amplified by PCR from facultatively lithotrophic aerobic COoxidizing bacteria, colorless and purple sulfide-oxidizing microbial mats, and genomic DNA extracts from tephra and ash deposits from Kilauea volcano, for which atmospheric CO and hydrogen have been previously documented as important substrates. PCR products from the mats and volcanic sites were used to construct rbcL clone libraries. Phylogenetic analyses showed that the rbcL sequences from all isolates clustered with form IC rbcL sequences derived from facultative lithotrophs. In contrast, the microbial mat clone sequences clustered with sequences from obligate lithotrophs representative of form IA rbcL. Clone sequences from volcanic sites fell within the form IC clade, suggesting that these sites were dominated by facultative lithotrophs, an observation consistent with biogeochemical patterns at the sites. Based on phylogenetic and statistical analyses, clone libraries differed significantly among volcanic sites, indicating that they support distinct lithotrophic assemblages. Although some of the clone sequences were similar to known rbcL sequences, most were novel. Based on nucleotide diversity and average pairwise difference, a forested site and an 1894 lava flow were found to support the most diverse and least diverse lithotrophic populations, respectively. These indices of diversity were not correlated with rates of atmospheric CO and hydrogen uptake but were correlated with estimates of respiration and microbial biomass.Several distinct functional groups comprise the bacterial lithotrophs. Obligate lithotrophs include sulfide-, sulfur-, metal-, ammonium-, and nitrite-oxidizing bacteria, many of which have been described in detail previously (2-5, 14-16, 28, 29, 35, 36, 39). In contrast, facultative lithotrophs include aerobic hydrogen-and CO-oxidizing bacteria, few of which have been described (22)(23)(24). Most facultative lithotrophs are heterotrophs that preferentially oxidize organic substrates or that grow mixotrophically with CO (or hydrogen) and organics (22,23). However, in spite of their physiological, ecological, and phylogenetic diversity, all lithotrophs are united by their ability to incorporate CO 2 for cell carbon through the activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO).RubisCO, the most abundant protein on Earth (33), has been thoroughly characterized (8,10,13,17,20,30,32,33,37,40). Based on various biochemical analyses, two forms have been documented. All known lithotrophic bacteria contain form I, while a relatively small number of bacteria, e.g., Hydrogenovibrio marinus, Rhodobacter capsulatus, Rhodobacter sphaeroides, and several Thiobacillus species, also contain form II (33). Sequence analyses of the gene coding for the large subunit of RubisCO (rbcL) have revealed two major phylogenetically distinct form I groups, a green alga-like group and a red alga...

Highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) provide nano-scale chemical fingerprints of the 2011 tragedy. U, Cs, Ba, Rb, K, and Ca isotopic ratios were determined on three CsMPs (3.79–780 Bq) collected within ~10 km from the FDNPP to determine the CsMPs’ origin and mechanism of formation. Apart from crystalline Fe-pollucite, CsFeSi2O6 · nH2O, CsMPs are comprised mainly of Zn–Fe-oxide nanoparticles in a SiO2 glass matrix (up to ~30 wt% of Cs and ~1 wt% of U mainly associated with Zn–Fe-oxide). The 235U/238U values in two CsMPs: 0.030 (±0.005) and 0.029 (±0.003), are consistent with that of enriched nuclear fuel. The values are higher than the average burnup estimated by the ORIGEN code and lower than non-irradiated fuel, suggesting non-uniform volatilization of U from melted fuels with different levels of burnup, followed by sorption onto Zn–Fe-oxides. The nano-scale texture and isotopic analyses provide a partial record of the chemical reactions that occurred in the fuel during meltdown. Also, the CsMPs were an important medium of transport for the released radionuclides in a respirable form.

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