A total of 108 pectolytic, soft-rotting Erwinia strains were collected from 11 types of cacti growing in Arizona, Texas, northern Mexico, and Australia between 1958 and. Four strains were collected from soils beneath or close to naturally rotting saguaro cacti. Collectively, these strains caused soft rots of saguaro, organ pipe, and senita cacti, Opuntia (cactus) fruits and pads, tomato fruits, and potato slices, but only occasionally caused soft rots of slices of carrot roots. A numerical cluster analysis showed that 98 of the 112 strains formed a uniform group (cluster 1A) that was distinguished from other pectolytic erwinias by an API 20E code of 1205131, by negative reactions in API 5OCHE tests for L-arabinose, myo-inositol, D-cellobiose, melibiose, and D-raffinose, and, in supplemental tests, by positive reactions for malonate and growth at 43°C. The average levels of DNA relatedness of 22 cluster 1A strains to the proposed type strain (strain 1-12) as determined by the hydroxyapatite method were 88% in 60°C reactions (with 1% divergence within related sequences) and 87% in 75°C reactions. The levels of relatedness to the type strains of other Erwinia spp. were 138% in 75°C reactions. Cluster 1A strains also had a characteristic cellular fatty acid profile containing cyclo-( 11,12)-nonadecanoic acid (C19:o cycle cll-lz) and missing tridecanoic acid (CI3J, heptadecanoic acid (C1,:o), and cis-9-heptadecenoic acid (Cl,:l g ) , which separated them from other pectolytic erwinias. Collectively, these data indicate that the members of cluster 1A are members of a new species, which we name Erwinia cacticida. Three cactus strains in cluster 1B appear to represent a second new species that is closely related to E. cacticida; these strains are designated E . cacticida-like pending the availability of additional strains for testing. The remaining cactus strains (in cluster 4) have the physiological, DNA, and fatty acid profiles of Erwinia carotovora.To our knowledge, Johnston and Hitchcock (22) were the first workers to describe a bacterial soft-rot disease of cacti in the United States. The cultures of these authors were isolated from prickly pear cacti (Opuntia tomentella Berger and OpuntiaJicus-indica (L.) Mill.) that were originally from Guatemala and Columbia but were growing in the U.S. Department of Agriculture plant introduction garden in Florida. The bacterium was briefly characterized as "an actively motile, gram-negative, aerobic, and facultative anaerobic bacillus" which produced an acid reaction when it was grown in broth containing "glucose, saccharose, mannite, and salicin but none in maltose, lactose, dulcite, and arabinose" (22). Subsequently, another new bacterial species, Erwinia carnegieana Standring 1942 (23), was described (3, 6, 23, 28) as being the causal agent of bacterial necrosis (a soft-rot disease) of saguaro cacti (Carnegiea gigantea Britt. & Rose). Among the soft-rot erwinias, this species was unique in that it was gram positive, a characteristic also noted by Boyle (6), and had a host ...

In vertebrates, cytochrome P450s of the CYP2 and CYP3 families play a dominant role in drug metabolism, while in insects members of the CYP6 and CYP28 families have been implicated in metabolism of insecticides and toxic natural plant compounds. A degenerate 3' RACE strategy resulted in the identification of fifteen novel P450s from an alkaloid-resistant species of Drosophila. The strong (17.4-fold) and highly specific induction of a single gene (CYP4D10) by the toxic isoquinoline alkaloids of a commonly utilized host-plant (saguaro cactus) provides the first indication that members of the CYP4 family in insects may play an important role in the maintenance of specific insect-host plant relationships. Strong barbiturate inducibility of CYP4D10 and two other D. mettleri P450 sequences of the CYP4 family was also observed, suggesting a pattern of xenobiotic responsiveness more similar to those of several vertebrate drug-metabolizing enzymes than to putative vertebrate CYP4 homologs.

Necrotic tissue of agria cactus (Stenocereus gummosus) serves as a feeding and breeding substrate for Drosophila mojavensis. This fly species is one of the four endemic Drosophila species in the Sonoran Desert. Freeze injuries were created in arms of agria cactus in Mexico to study the events of microbial colonization. Facultative anaerobic bacteria were the first microbes to be detected, and the exclusion of large arthropods by covering the injuries with netting did not affect bacterial colonization. Yeast growth lagged behind bacterial growth by 2 days, and excluding arthropods delayed the detection of yeasts by an additional 2 days. Thus, insects (such as Drosophila species) and other arthropods do play a role in the colonization of agria rots by yeasts. All injuries were attractive to D. mojavensis within 5 days, and these flies were shown to be carrying significant densities of both bacteria and yeasts. Analysis of the volatile compounds present in the developing rots over time indicated that the volatile pattern is dynamic. Ethanol and acetic acid were the two volatile substances most likely responsible for the initial attraction of the injuries for Drosophila species.

To compare the bacterial communities residing in necrotic tissues of columnar cacti of the Sonoran Desert, isolates from 39 organ pipe, 19 saguaro, and 16 senita cacti were obtained. The isolates were clustered into 28 conspecific groups on the basis of their fatty acid profiles. The distributions of the individual bacterial isolates varied among cactus species. Seven of the 28 species groups were unique to a particular cactus species, whereas 8 species groups were found in all three cacti. The effective number of bacterial species for each cactus species was positively correlated with both the chemical complexity and glucose concentration of the plant tissues. The effective number of bacterial species and bacterial distribution patterns were compared with those known for communities of cactophilic yeasts. The observed bacterial distribution patterns are most likely due to differences in the chemical compositions of the three cactus species.

The cytochrome P450s comprise a superfamily of mostly microsomal haemoproteins which play a dominant role in the metabolism of a variety of endogenous and foreign compounds. The use of a degenerate PCR primer targeted to the haem-binding decapeptide unique to the cytochrome P450 superfamily resulted in the identification of 14 novel cytochrome P450s in the Mediterranean Fruit Fly, Ceratitis capitata. Analysis of the relative frequency of individual isoforms within the pool of isolated sequences suggests that the CYP4 and CYP6 P450 families contain the most highly expressed isoforms in adult C. capitata. Phylogenetic analyses of the conceptual amino acid translations of PCR-amplified cDNAs provides evidence that one of isolated sequences may represent a new P450 family.