Brucella melitensis is a facultative intracellular bacterial pathogen that causes abortion in goats and sheep and Malta fever in humans. The genome of B. melitensis strain 16M was sequenced and found to contain 3,294,935 bp distributed over two circular chromosomes of 2,117,144 bp and 1,177,787 bp encoding 3,197 ORFs. By using the bioinformatics suite ERGO, 2,487 (78%) ORFs were assigned functions. The origins of replication of the two chromosomes are similar to those of other ␣-proteobacteria. Housekeeping genes, including those involved in DNA replication, transcription, translation, core metabolism, and cell wall biosynthesis, are distributed on both chromosomes. Type I, II, and III secretion systems are absent, but genes encoding sec-dependent, sec-independent, and flagellaspecific type III, type IV, and type V secretion systems as well as adhesins, invasins, and hemolysins were identified. Several features of the B. melitensis genome are similar to those of the symbiotic Sinorhizobium meliloti.

The potential use of Bacillus anthracis as a weapon of mass destruction poses a threat to humans, domesticated animals, and wildlife and necessitates the need for a rapid and highly specific detection assay. We have developed a real-time PCR-based assay for the specific detection of B. anthracis by taking advantage of the unique nucleotide sequence of the B. anthracis rpoB gene. Variable region 1 of the rpoB gene was sequenced from 36 Bacillus strains, including 16 B. anthracis strains and 20 other related bacilli, and four nucleotides specific for B. anthracis were identified. PCR primers were selected so that two B. anthracis-specific nucleotides were at their 3 ends, whereas the remaining bases were specific to the probe region. This format permitted the PCR reactions to be performed on a LightCycler via fluorescence resonance energy transfer (FRET). The assay was found to be specific for 144 B. anthracis strains from different geographical locations and did not cross-react with other related bacilli (175 strains), with the exception of one strain. The PCR assay can be performed on isolated DNA as well as crude vegetative cell lysates in less than 1 h. Therefore, the rpoB-FRET assay could be used as a new chromosomal marker for rapid detection of B. anthracis.Bacillus anthracis is a causal agent of anthrax, a serious and often fatal infection of livestock and humans. It is considered one of the most effective biological weapons of mass destruction because of its highly pathogenic nature and spore-forming capability and has attracted attention due to its potential use as a biological warfare agent (2). This bacterium can infect humans by cutaneous, gastrointestinal, or respiratory routes. The standard laboratory method of identification takes advantage of the lytic nature of the B. anthracis-specific gamma bacteriophage (9). Anthrax bacilli are often distinguished on the basis of time-consuming morphological or phenotypic characteristics, such as gram-positive staining, spore-forming capability, nonhemolytic reaction on sheep blood agar, sensitivity to penicillin, nonmotile nature, and inability to ferment salicin (11). B. anthracis is distinguished from the other members of the closely related Bacillus cereus group of bacteria by the presence of the toxin-encoding pXO1 (19, 24) and capsule-encoding pXO2 plasmids (14,23,34). Both plasmids are needed for virulence; thus, the absence of either plasmid results in attenuation.B. anthracis, Bacillus thuringiensis, B. cereus, and Bacillus mycoides, are members of the B. cereus group of bacilli. These closely related bacteria are pathogens of mammals (B. anthracis and B. cereus) and insects (B. thuringiensis). The B. cereus group is one of the most taxonomically ambiguous group of bacilli (27). In fact, DNA-DNA hybridization (30) and pulsedfield gel electrophoresis (15) have shown great homology among B. anthracis, B. thuringiensis, and B. cereus. A recent multilocus enzyme electrophoresis study has concluded that the members of this group belong to one species (16)....

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The genome of Bacillus anthracis is extremely monomorphic, and thus individual strains have often proven to be recalcitrant to differentiation at the molecular level. Long-range repetitive element polymorphism-PCR (LR REP-PCR) was used to differentiate various B. anthracis strains. A single PCR primer derived from a repetitive DNA element was able to amplify variable segments of a bacterial genome as large as 10 kb. We were able to characterize five genetically distinct groups by examining 105 B. anthracis strains of diverse geographical origins. All B. anthracis strains produced fingerprints comprising seven to eight bands, referred to as "skeleton" bands, while one to three "diagnostic" bands differentiated between B. anthracis strains. LR REP-PCR fingerprints of B. anthracis strains showed very little in common with those of other closely related species such as B. cereus, B. thuringiensis, and B. mycoides, suggesting relative heterogeneity among the non-B. anthracis strains. Fingerprints from transitional non-B. anthracis strains, which possessed the B. anthracis chromosomal marker Ba813, scarcely resembled those observed for any of the five distinct B. anthracis groups that we have identified. The LR REP-PCR method described in this report provides a simple means of differentiating B. anthracis strains. Anthrax is often a fatal bacterial infection that results afterBacillus anthracis spores enter a suitable host either via inhalation or ingestion or through the contamination of a wound or abrasion (8). Since death occurs within a few days after the onset of symptoms, B. anthracis presents a very serious threat if deployed as a biological weapon (13). Naturally occurring human B. anthracis infections are rare and generally result from contact with contaminated animals or their products (5).Due to the highly monomorphic nature of B. anthracis, differentiation of strains from diverse origins has proven to be very difficult. DNA fingerprinting of B. anthracis strains using ribotyping has shown some strain-to-strain variations, presumably due to changes in the organization and number of rrn loci (18). However, due to insufficient numbers of variant strains, ribotyping was found to have limited discriminatory potential.Neither arbitrarily-primed PCR fingerprints (1) nor amplified fragment length polymorphisms fingerprints (15) have been useful in discriminating between B. anthracis strains, although some genetic diversity has been observed. In this case, the diversity was due to the presence of a variable-number tandem repeat (14) sequence in the open reading frame (ORF) vrrA. Recently, seven additional loci containing these sequences were discovered in B. anthracis, leading to the identification of six genetically distinct groups of B. anthracis (16).The presence of multiple copies of highly conserved repetitive extragenic palindromic (REP) sequences in DNA (12) has been identified in a number of microorganisms (28). The technique of REP-PCR takes advantage of the fact that multiple copies of these REP sequences...