The incidence of Weeksella- and Bergeyella-like bacteria in the food environment

Eighty-five catalase- and oxidase-positive Gram-negative rods and cocci susceptible to penicillin G were isolated from a variety of food sources. The phenotypic relationships of these isolates with reference cultures of Bergeyella -like, Chryseobacterium, Empedobacter, Myroides , Moraxella , Sphingobacterium and Weeksella -like strains were examined by numerical taxonomy. Seventy-three isolates were recovered in five groups; 80% of the isolates clustered in groups 1, 2 and 3 and produced indole, bearing a strong resemblance to Weeksella and Bergeyella . They could not, however, be regarded as belonging to the known species of W. virosa and B. zoohelcum . It is suggested that three species may be necessary to accommodate the environmental Weeksella - or Bergeyella -like bacteria. The isolates in groups 4 and 5 had white colonies and were unable to produce indole, in this way resembling the Moraxella genus.     

Recombinant plasmid conferring proline overproduction and osmotic tolerance.

A recombinant plasmid carrying the proBA (pro-74) mutant allele which governs osmotic tolerance and proline overproduction was constructed by using the broad-host-range plasmid vector pQSR49. The physiological, biochemical, and genetic properties of strains carrying the pQSR49 derivatives pMJ101 and pMJ1, mutant and wild type, respectively, were investigated. pMJ101 conferred enhanced osmotolerance compared with strains carrying the wild type, pMJ1. These results are in contrast to those obtained previously with strains carrying recombinant plasmids based on pBR322 that failed to confer the osmotic tolerance phenotype. gamma-Glutamyl kinase (first step in proline biosynthesis) from strains carrying pMJ101 was 200-fold less sensitive to feedback inhibition than was the wild-type enzyme. As expected, the intracellular proline levels of strains carrying pMJ101 were more than an order of magnitude higher than those of the wild type. An analysis of copy number revealed that the pQSR49 constructs were present in the cell at a level six- to eightfold lower than those of the pBR322 recombinants, which may account for the difference in phenotype. We found that the genetic stability of the pQSR49 derivative in a variety of gram-negative bacteria was dependent on the insert orientation and the presence of foreign DNA on the plasmid. These factors may be significant in future studies aimed at expanding the osmotolerance phenotype to a broad range of gram-negative bacteria.     

Heliothrix oregonensis,gen. nov., sp. nov., a phototrophic filamentous gliding bacterium containing bacteriochlorophyll a

An unusual filamentous, gliding bacterium was found in a few hot springs in Oregon where it formed a nearly unispecific top layer of microbial mats. It contained a bacteriochlorophyll a-like pigment and an abundance of carotenoids. There were no chlorosomes or additional chlorophylls. The organism was aerotolerant and appeared to be photoheterotrophic. It was successfully co-cultured with an aerobic chemoheterotroph in a medium containing glucose and casamino acids. Although it has many characteristics in common with the genus Chloroflexus, the lack of chlorosomes and bacteriochlorophyll c and the aerobic nature of this organism indicate that it should be placed in a new genus. This conclusion is supported by 5S rRNA nucleotide sequence data.     

An approach to the focal presentation of chemical stimuli

An olfactometer is described that presents temporally-discretepulses of stimuli to individual chemosensory structures. Thedevice is based on standard pressure injection techniques inwhich pulses of compressed air eject nanoliter volumes of upto six stimulants from small diameter glass micropipettes. Thedevice should be readily adaptable to different chemoreceptorpreparations.