No abstract

cTransmission of Yersinia pestis is greatly enhanced after it forms a bacterial biofilm in the foregut of the flea vector that interferes with normal blood feeding. Here we report that the ability to produce a normal foregut-blocking infection depends on induction of the Y. pestis PhoP-PhoQ two-component regulatory system in the flea. Y. pestis phoP-negative mutants achieved normal infection rates and bacterial loads in the flea midgut but produced a less cohesive biofilm both in vitro and in the flea and had a greatly reduced ability to localize to and block the flea foregut. Thus, not only is the PhoP-PhoQ system induced in the flea gut environment, but also this induction is required to produce a normal transmissible infection. The altered biofilm phenotype in the flea was not due to lack of PhoPQ-dependent or PmrAB-dependent addition of aminoarabinose to the Y. pestis lipid A, because an aminoarabinose-deficient mutant that is highly sensitive to cationic antimicrobial peptides had a normal phenotype in the flea digestive tract. In addition to enhancing transmissibility, induction of the PhoP-PhoQ system in the arthropod vector prior to transmission may preadapt Y. pestis to resist the initial encounter with the mammalian innate immune response.

No abstract

Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr) based on their efficacy and cost-effectiveness in the production of tomato (Solanum lycopersicum). The analysis was conducted for the mountain tomato production region based on 6 years of field test data collected in Fletcher, NC. Fumigation alternatives evaluated included 61.1% 1,3-dichloropropene + 34.7% chloropicrin (Telone-C35™), 60.8% 1,3-dichloropropene + 33.3% chloropicrin (InLine), 99% chloropicrin (Chlor-o-pic), 94% chloropicrin (TriClor EC), 42% metam sodium (4.26 lb/gal a.i., Vapam), and 50% iodomethane + 50% chloropicrin (Midas). The MeBr formulation was 67% methyl bromide and 33% chloropicrin (Terr-O-Gas). Chloropicrin applied at 15 gal/acre provided the greatest returns with an additional return of $907/acre relative to MeBr. Telone-C35 provided an additional return of $848/acre and drip-applied metam sodium provided an additional return of $137/acre. The return associated with broadcast applied metam sodium was about equal to the estimated return a grower would receive when applying MeBr. Fumigating with a combination of chloropicrin and metam sodium; shank-applied chloropicrin at 8 gal/acre; drip-applied chloropicrin, Midas, or InLine; and the nonfumigated soil treatment all resulted in projected losses of $156/acre, $233/acre, $422/acre, $425/acre, $604/acre, and $2133/acre, respectively, relative to MeBr. Although technical issues currently associated with some of the MeBr alternatives may exist, results indicate that there are economically feasible fumigation alternatives to MeBr for production of tomatoes in North Carolina.