VNTR loci reveal differentiation between and structure within populations of the eastern barred bandicoot Perameles gunnii

The Eastern Barred Bandicoot Perameles gunnii has declined in abundance within mainland south-eastern Australia, to a relict wild population of less than 100 individuals in Hamilton, Victoria. It is more common, but is also declining in Tasmania. Genomic DN A variability was compared within and between surviving populations of P. gunnii using variable number of tandem repeat (VNTR) markers in one of two ways. First, average percentage differences (APDs) were determined between profiles for two VNTR probe—endonuclease combinations. Secondly, because one of these combinations revealed two multiallelic VNTR loci, genotypes were assigned and analysed for homogeneity of allele frequencies among subpopulations, for deviation of heterozygosity from Hardy-Weinberg equilibrium within populations and for genetic structuring among individuals from different subpopulations. The results of both the APD and defined locus approaches showed consistent trends within and between populations. Genetic variability was higher among mainland P. gunnii than in Tasmanian populations (higher APDs, number of alleles, and heterozygosity at one locus), despite the known decline and subdivision of the Hamilton population. Eleven per cent of the variability detected in Hamilton was attributed to genetic differentiation between east and west subdivisions of the population. Departure from random mating indicating local inbreeding within collecting localities was evident for one locus in both north and south Tasmania, particularly at one locality. AH alleles at both loci were unique to either Hamilton or Tasmanian P. gunnii. The initial captive colony contains high heterozygosity for these loci. It is concluded that VNTR markers can be of benefit for use in studies of population differentiation and for conservation management.     

The quantitative assessment of arthropod predation rates by electrophoresis

The development of an electrophoretic technique for the quantitative assessment of specific prey material in the gut of a predator is described. Panonychus ulmi and Tetranychus urticae were used as test prey species. Samples prepared from these mites were electrophoresed on polyacrylamide concentration gradient slab gels, which were then treated to reveal esterase activity. The relationship of intensity of a stained band with sample concentration and staining time was not linear for some esterases. Possible causes of this non-linearity were identified but could not readily be eliminated. However, quantitative assessment of prey material is possible after the preparation of a calibration curve.     

Photorespiratory Amino Donors, Sucrose Synthesis and the Induction of CO2 Fixation in Barley Deficient in Glutamine Synthetase and/or Glutamate Synthase

Murray, A. J. S., Black well, R. D., Lea, P. J. and Joy, K.W. 1988. Photorespiratory amino donors, sucrose synthesis andthe induction of CO₂ fixation in barley deficient in glutaminesynthetase and/or glutamate synthase.—J. exp. Bot. 39:845–858. A number of mutants of barley have been produced which lackboth chloroplastic glutamine synthetase and ferredoxin-dependentglutamate synthase activities. The plants accumulated ammoniato the same extent as mutants deficient in only glutamine synthetasebut shared the gas-exchange characteristics of the glutamatesynthase deficient parent. These mutants have been used to demonstratedirectly the ability of alanine to ameliorate the dramatic dropin fixation rate normally exhibited by glutamate synthase deficientmutants on transfer to photorespiratory conditions. Immediatelyafter transfer to air, the mutants deficient in glutamate synthaseactivity demonstrated a reduced ability to incorporate ¹⁴C derivedfrom ¹⁴CO₂ into sucrose. This effect was, however, dependenton the previous induction of CO₂ fixation. Use of ¹⁴CO₂ revealedthat the induction phase of CO₂ fixation was altered in allthree mutants. Neither of the parents nor the double mutantaccumulated sucrose in air under conditions which promote sucroseaccumulation by the wild type. The implications of these resultsfor photosynthesis and the control of sucrose synthesis arediscussed. Key words: Photorespiratory barley mutant, amino donors, sucrose, GS, glutamate synthase.     

Karyotypes and C-banding patterns in species of Cyphomandra Mart, ex Sendtner (Solanaceae)

The orcein and C-banded karyotypes of 11 species of Cyphomandra (Solanaceae) were described. All species were diploid with 2n = 2x = 24. The chromosomes were large, ranging from 4 to 10 u.m iⁿ length, and in each complement were largely metacentric or submetacentric with few subtelocentrics. There was a significant negative correlation between chromosome length and arm ratio within a complement as well as between taxa. In general, chromosomes of the larger complements were more symmetrical in terms of both relative chromosome length and arm ratio, implying that similar amounts of DNA had been added to or taken away from every chromosome are of each complement during evolutionary divergence. Two pairs of non-homologous chromosomes were seen to contain subterminal secondary constrictions in most species. The two Brazilian species studied differed from those of Andean origin in the location of one of these secondary constrictions, suggesting a major evolutionary divergence between these two groups of specieS. Non-homologous chromosomes were difficult to distinguish from one another without the aid of C-banding, due to a continuum in the distribution of chromosome lengths and arm ratios. Telomeric and interstitial bands were shown in all species but not all chromosomes in each complement were banded. There were no centromeric bandS. Nuclear DNA amount and the length, but not proportional length, of C-bands were correlated in each specieS. One species ( C. Luteoalba (Pers.) Child, section Cyphomandropsis ) was unique in its banding pattern, providing further evidence for the delimitatation of this species and perhaps section from other Cyphomandra taxa.     

Some Metabolic and Biochemical Characteristics of Representative Microbial Isolates from Vacuum-packaged Beef

Some of the metabolic and biochemical characteristics of 105 organisms isolated at 4° from meat matured in vacuo at 0–2° for 0–9 weeks were studied. Proteolysis was noted in Pseudomonas spp., Achromobacter spp. and Gram negative, fermentative organisms, mainly in aerobic and low oxygen environments. Fewer organisms hydrolysed beef fat than hydrolysed tributyrin. While representatives of most of the major groups of organisms dissimilated mono- and di-saccharides, more complex carbohydrates were less readily attacked. Only Gram negative, fermentative organisms showed decarboxylase activity on amino acids. There is evidence that Pseudomonas spp. can survive in an anaerobic environment, although their metabolism is less vigorous.