A new species, Bacillus azotojixans, is described. This taxon is based upon 16 soil and root-associated strains that exhibit acetylene-reducing ability and nitrogen-fixing Bacillus sp. strain Hino. B . azotojixans is phenotypically similar to Bacillus polymyxa and Bacillus macerans. However, 13 tests (nitrate reduction; production of acid and gas from xylose, arabinose, lactose, ribose, and glycerol; resistance to lysozyme; liquefaction of gelatin; starch hydrolysis; decomposition of casein and pectin; production of dihydroxyacetone; susceptibility to B . polymyxa phages) differentiate it from B. polymyxa, and 12 characteristics (spore position; Voges-Proskauer test; nitrate reduction; production of acid and gas from xylose, arabinose , lactose, ribose, and glycerol; growth at 45°C; hydrolysis of starch; decomposition of pectin; formation of crystalline dextrins) differentiate it from B. macerans. The guanine-plus-cytosine contents of five strains ranged from 47.9 to 52.5 mol%. All strains reduced acetylene much more efficiently than B. polymyxa or B . macerans. In four strains, nitrogen fixation was confirmed by micro-Kjeldahl analysis of acetylene-reducing cultures. Acetylene reduction was not inhibited by nitrate and was not dependent on yeast extract or thiamin plus biotin. The proposed type strain of B. azotojixans is strain P3L-5 (= ATCC 35681).Classically, all Bacillus strains capable of fixing molecular nitrogen were found to belong to Bacillus polymyxa (7, 9) or Bacillus macerans (23). In later work, other (nonsymbiotic) nitrogen-fixing Bacillus isolates were tentatively identified as strains of Bacillus circulans (10). To date, no strains of other Bacillus species have been accepted with certainty as nitrogen fixers, although recently it was claimed that several nitrogen-fixing bacilli resembled Bacillus cereus or Bacillus licheniformis (1). Most of the recently isolated nitrogenfixing bacilli have been identified clearly as B. polymyxa (16)(17)(18)(19)(20) or B. macerans strains (17) or as B . polymyxa-like (24) organisms. The original work of Hino and Wilson (9) on nitrogen fixation by a Bacillus strain was done with an isolate that has been classified as an atypical B. polymyxa strain (4, 14, 19). However, the deoxyribonucleic acid (DNA) of this strain revealed a guanine-plus-cytosine (G + C) content beyond the range reported for B. polymyxa, which is typical of B . macerans (14).In a previous report (20), we described 18 acetylenereducing B . polymyxa strains from soil and 6 other strains with this property that were tentatively identified as "variants" of B . polymyxa. Since then, 10 other acetylenereducing bacilli have been isolated in our laboratory from washed or surface-sterilized roots of different grasses; these strains had properties that were remarkably similar to those of the six aforementioned isolates. In this paper, we describe the characteristics of all of the strains belonging to this group of nitrogen-fixing bacilli. MATERIALS AND METHODSBacterial strains. The strains used and their...

The genetic basis of bacteriocin (Bac) production by six strains of Stuphylococcus aureus was examined. Gene transfer experiments (in which the plasmids were tagged with the erythromycin resistance transposon Tn551) and plasmid-elimination experiments by growth at 43 "C associated bacteriocin production with a particular plasmid in each strain. The Bac plasmids could be separated into two distinct groups: the first comprised plasmids larger than 40 kb, which did not specify immunity to bacteriocins; the second comprised small plasmids (8.0-10-4 kb) which also specified immunity to bacteriocins. The sequence relations among the small plasmids (pRJ6, pRJ9, pRJlO and pRJ11) were investigated by comparing restriction enzyme digest patterns and by hybridization. Plasmids pRJlO and pRJ11 were indistinguishable and very closely related to plasmid pRJ9. Plasmid pRJ6, although different from the others, shared regions of sequence homology with them. No homology was found between plasmids pRJ6 or pRJ9 and the large Bac plasmids.

Five different Brazilian soils were examined for the incidence of Bacillus nitrogen fixers. These counts were set in relation to the total spore count, and the number of facultative anaerobic spores. Twenty-four Bacillus strains were isolated using media lacking a nitrogen source, identified and their acetylene-reducing ability was determined. Eighteen of these strains were identified as B. polymyxa, and the other 6 were related to this species, but were different in some taxonomical tests, Of the 24 isolated strains, only 13 reduced acetylene; similarly, only 3 out of 9 B. polymyxa reference strains were able to reduce acetylene.

The identification of Bacillus azotofixans strains using API tests is described. Twenty-two strains were studied according to their fermentation pattern on 49 different carbohydrates. A profile of the B. azotofixans type strain is presented, together with an average profile of all strains tested. The fermentation pattern for B. azotofixans is also compared to those of the closely similar species B. polymyxa and B. macerans. These profiles may be useful for the identification of new strains.

Salmonella typhosa hybrids able to adsorb lambda were obtained by mating S. typhosa recipients with Escherichia coli K-12 donors. After adsorption of wild-type λ to these S. typhosa hybrids, no plaques or infective centers could be detected. E. coli K-12 gal + genes carried by the defective phage λ dg were transduced to S. typhosa hybrids with HFT lysates derived from E. coli heterogenotes. The lysogenic state which resulted in the S. typhosa hybrids after gal + transduction differed from that of E. coli . Ability to produce λ, initially present, was permanently segregated by transductants of the S. typhosa hybrid. S. typhosa lysogens did not lyse upon treatment for phage induction with mitomycin C, ultraviolet light, or heat in the case of thermoinducible λ. A further difference in the behavior of λ in Salmonella hybrids was the absence of zygotic induction of the prophage when transferred from E. coli K-12 donors to S. typhosa . A new λ mutant class, capable of forming plaques on S. typhosa hybrids refractory to wild-type λ, was isolated at low frequency by plating λ on S. typhosa hybrid WR4254. Such mutants have been designated as λ sx , and a mutant allele of λ sx was located between the P and Q genes of the λ chromosome. Plaques were formed also on the S. typhosa hybrid host with a series of λ i21 hybrid phages which contain the N gene of phage 21. The significance of these results in terms of Salmonella species as hosts for λ is discussed.