A previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the Northern Territory of Australia. The organism, designated NT-26, was found to be a gram-negative motile rod with two subterminal flagella. In a minimal medium containing only arsenite as the electron donor (5 mM), oxygen as the electron acceptor, and carbon dioxide-bicarbonate as the carbon source, the doubling time for chemolithoautotrophic growth was 7.6 h. Arsenite oxidation was found to be catalyzed by a periplasmic arsenite oxidase (optimum pH, 5.5). Based upon 16S rDNA phylogenetic sequence analysis, NT-26 belongs to the Agrobacterium/Rhizobium branch of the ␣-Proteobacteria and may represent a new species. This recently discovered organism is the most rapidly growing chemolithoautotrophic arsenite oxidizer known.Arsenic is found in many environments and is toxic to life in some forms. When present in insoluble forms, which are nontoxic, arsenic is frequently found as a mineral in combination with sulfur (e.g., orpiment [As 2 S 3 ] and realgar [AsS]) and especially with iron and sulfur (e.g., arsenopyrite [FeAsS]). The oxidation of these insoluble forms, chemically and/or microbiologically, results in the formation of arsenite (As III [H 3 AsO 3 ]). In environments such as acid mine drainage, arsenite concentrations can be extremely high (2 to 13 mg/liter) (22). The arsenite formed in various environments can then be oxidized to arsenate (As V [H 2 AsO 4 Ϫ ϩ H ϩ ]). Both of these soluble forms of arsenic, arsenite and arsenate, are toxic to living organisms, with arsenite considered more toxic than arsenate (5, 22).Interestingly, the chemical oxidation of arsenite to arsenate is slow. Most arsenite is, therefore, oxidized to arsenate microbiologically (22). Arsenite-oxidizing bacteria were first described in 1918 (7). These organisms, as well as a number of others that have been isolated more recently, are almost all heterotrophic arsenite-oxidizing bacteria, as they require the presence of organic matter for growth (17,18,23,24). The most common organism found has been Alcaligenes faecalis (7,17,18,23,24). For these heterotrophic bacteria, the oxidation (equation 1) is considered a detoxification mechanism rather than one that can support growth, despite the fact that the reaction is exergonic.Only one bacterium has been described that is able to use the energy gained from this reaction for growth. This organism, Pseudomonas arsenitoxidans, was found to grow chemolithoautotrophically with arsenite, oxygen, and carbon dioxide. The fastest doubling time reported for growth with arsenite was, however, in the order of 2 days (8). This report describes a new bacterium, isolated from a gold mine in the Northern Territory of Australia, that can also grow chemolithoautotrophically with arsenite as the electron donor, oxygen as the electron acceptor, and carbon dioxide (CO 2 ) or bicarbonate (HCO 3 Ϫ ) as the carbon source. Growth was rapid, with a doubling time of 7.6 h for chemolithoautotrophic grow...

Polyacrylamide gel electrophoretic analysis of purified preparations of human and calf diarrhea viruses indicated eight polypeptide components, or possibly nine in the case of the calf diarrhea virus. Thermal denaturation and analytical studies of the calf diarrhea virus genome showed it to consist of 11 doublestranded segments of RNA. The placing of the human and calf diarrhea viruses together with other similar viruses into a genus separate from reovirus and orbivirus, but within the family Reoviridae, is discussed.

Polyacrylamide gel electrophoretic analysis of purified preparations of the simian rotavirus SA-11 indicated eight polypeptide components that migrated in a manner remarkably similar to those of the previously characterized human and calf rotaviruses. Analyses of preparations of single-shelled and doubleshelled particles of human, calf, and simian rotaviruses have also permitted assignment of the polypeptides to the inner or outer shells. The major components of the outer shells of each virus have been identified as glycoproteins, and the importance of this in terms of host cell specificity is discussed. Sensitivities of the various rotaviruses to acid, proteases, and glycosidases were also investigated.

The effect of lactoferrin and prostaglandins E and F2 alpha on the growth of rotavirus and respiratory syncytial virus in cell culture was investigated. Lactoferrin inhibited the growth of respiratory syncytial virus at a concentration tenfold lower than that normally present in human milk. The prostaglandins had no effect on either virus growth, even at a concentration of 100-fold more than that found in human milk. Lactoferrin may have some antiviral properties in human milk in addition to its known antibacterial functions.

Group C rotaviruses have been identified recently from fecal samples of children with diarrhea in the United States. Using reverse transcriptasepolymerase chain reaction and sequence analysis, we sequenced gene 8s encoding VP7 from two U.S. strains (RI-1 and RI-2), and eight other strains isolated from patients on four continents, and compared these with the sequences of four published strains. The gene 8s of the 14 strains were remarkably conserved in size and in predicted primary and secondary structures. When the sequences of the human VP7s were compared with that of the prototype porcine Cowden strain, six regions were found variable in both deduced primary and predicted secondary structures, four of which were predicted to be hydrophilic and might determine serotype specificity. Gene 8 of the human S-1 strain was further characterized by expression in recombinant baculoviruses. The expressed product was immunogenic but failed to elicit neutralizing antibodies. Our sequence analysis indicates that all the human strains characterized to date belong to a single G genotype, which may constitute a single G serotype, pending further antigenic analysis. Whether the human strains and the Cowden strain are the same serotype remains to be determined.