From a potentiometric
and visible spectrophotometric study of the
nickel(II)-citric acid (H3L) system in the pH range 3-6, four
complexes, NiL-, NiHL,
NiH2L+ and NiL24-, have been
characterized. Stability constants for the formation of these complexes have
been determined at 25°C in 0.1 mol dm-3 KCl.
The results suggest that the hydroxy group of citric acid is coordinated in the
nickel-citrate complexes.
Stackhousia tryonii Bailey, which appears to be endemic to the serpentinite soils of the Port Curtis
district, central Queensland, is a hyper-accumulator of nickel. Concentrations of this element reach
1-20% of the dry weight of the leaves and 0.1-1% in other parts of the plant. This is the first discovery
of such behaviour in a plant from eastern Australia. S. tryonii is easily distinguishable from the Queensland
occurrences of a related species, S. monogyna Labill., by its smaller inflorescences and muchbranched,
tufted, slender stems and distinctive sparsely tuberculate seed coat. S. monogyna shows no
abnormal nickel accumulation. Detailed diagnostic comparative descriptions of S. tryonii and
S. monogyna are provided, and notes are given on the ecology and distribution of the two species.
Aims: To examine the prevalence of bacteriocin production in Streptococcus bovis isolates from Australian ruminants and the feasibility of industrial production of bacteriocin.
Methods and Results: Streptococcus bovis strains were tested for production of bacteriocin‐like inhibitory substances (BLIS) by antagonism assay against Lactococcus lactis. BLIS production was associated with source animal location (i.e. proximity of other bacteriocin‐positive source animals) rather than ruminant species/breed or diet. One bacteriocin showing strong inhibitory activity (Sb15) was isolated and examined. Protein sequence, stability and activity spectrum of this bovicin were very similar to bovicin HC5. Production could be increased through serial culturing, and increased productivity could be partially maintained during cold storage of cultures.
Conclusions: BLIS production is geographically widely distributed in Eastern Australia, and it appears that the bacteriocin+ trait is maintained in animals at the same location. The HC5‐like bacteriocin, originally identified in North America, is also found in Australia. Production of bacteriocin can be increased through serial culturing.
Significance and Impact of the Study: The HC5‐like bacteriocins appear to have a broad global distribution. Serial culturing may provide a route towards commercial manufacturing for use in industrial applications, and purified bacteriocin from S. bovis Sb15 could potentially be used to prevent food spoilage or as a feed additive to promote growth in ruminant species.
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