Sensitivity of the Burkholderia cepacia complex and Pseudomonas aeruginosa to transducing bacteriophages

Burkholderia cepacia is now recognised as a life-threatening pathogen among several groups of immunocompromised patients. In this context, the proposed large-scale use of these bacteria in agriculture has increased the need for a better understanding of the genetics of the species forming the B. cepacia complex. Until now, little information has been available on the bacteriophages of the B. cepacia complex. Transducing phages, named NS1 and NS2, were derived from the lysogenic B. cepacia strains ATCC 29424 and ATCC 17616. The frequency of transduction per phage particle ranged from 1.0x10(-8) to 7.0x10(-6) depending on the phage and recipient strain used. The host range of NS1 and NS2 differed but in each case included environmental and clinical isolates, and strains belonging to several species and genomovars of the B. cepacia complex. The host range of both phages also included Pseudomonas aeruginosa. Some B. cepacia complex isolates were sensitive to the well-characterised P. aeruginosa transducing phages, B3, F116L and G101. The lytic activity of NS1 and NS2 was inhibited by B. cepacia lipopolysaccharide suggesting that this moiety is a binding site for both phages. The molecular size of the NS1 and NS2 genomes was approximately 48 kb.     

Phosphorus inputs to Lake Naivasha,Kenya, from its catchment and the trophic state of the lake

The main river supplying Lake Naivasha, Kenya, the Malewa, drains a catchment given over to largely subsistence cultivation and animal husbandry. The lake itself is the focus for an intensive horticultural industry based upon irrigation from the lake. The Malewa, however, is relatively independent of the impact of industry, and so its contribution to eutrophication of the lake was evaluated. Two periods of study, a very wet-dry and a `normal' wet-dry season showed that the river contribution of phosphorus led to a total phosphorus loading of 1.4 g m<sup>–2</sup> lake surface ann<sup>–1</sup> in the very wet period compared to 0.2 in the `normal'. Chlorophyll `a' in the open water of the lake was significantly related to soluble reactive phosphorus. The lake is now eutrophic by normal limnological criteria.     

Burkholderia anthina sp. nov. and Burkholderia pyrrocinia,two additional Burkholderia cepacia complex bacteria,may confound results of new molecular diagnostic tools

Nineteen Burkholderia cepacia-like isolates of human and environmental origin could not be assigned to one of the seven currently established genomovars using recently developed molecular diagnostic tools for B. cepacia complex bacteria. Various genotypic and phenotypic characteristics were examined. The results of this polyphasic study allowed classification of the 19 isolates as an eighth B. cepacia complex genomovar (Burkholderia anthina sp. nov.) and to design tools for its identification in the diagnostic laboratory. In addition, new and published data for Burkholderia pyrrocinia indicated that this soil bacterium is also a member of the B. cepacia complex. This highlights another potential source for diagnostic problems with B. cepacia-like bacteria.     

Chemical characteristics,with particular reference to phosphorus,of the rivers draining into Lake Naivasha,Kenya

The loss of phosphorus from the catchment of Lake Naivasha, Kenya, was 0.2 kg ha^–1 ann^–1, 76% of it particulate in a `normal' year of wet and dry periods. It rose to a mean of 1.8 kg ha^–1 ann^–1, 90% of which was particulate, in the months following the extreme rainfall which followed the 1997–1998 El Niño event in the Southern Atlantic. Total and particulate phosphorus were positively correlated with suspended solids and with discharge, and conductivity was negatively correlated with discharge. The magnitude of losses pose both threats to the water quality of Lake Naivasha and to the sustainable soils resources of the catchment.