Suburban development and change in vegetation nutritional status

In a study of species presence/absence and soil properties in bushland around northern Sydney, Clements (1983) found that species groupings were related to total soil phosphorus. This report presents analysis of foliage nutrient concentrations in species within these groupings. The highest concentrations of phosphorus, calcium, magnesium and potassium occurred in the suburban/disturbed group. The lowest overall concentrations were found in foliage from species in the dry sclerophyll communities. Mean foliage phosphorus was 0.099%, 0.125% and 0.042% for wet sclerophyll, disturbed and dry sclerophyll groups, respectively. Exotic species, particularly in disturbed environments, had the highest foliage nutrient concentrations. Results presented here showed that foliage nutrient concentrations are consistent with definitions of these groups on the basis of total soil phosphorus. These changes are considered to be important for management and conservation of bushland areas around Sydney.     

ROUTINE RESAZURIN TEST RESULTS AND THERMODURIC BACTERIAL CONTENT OF MILK SAMPLES AS A MEASURE OF MILK PRODUCTION CONDITIONS

The milk production conditions on 44 farms (18 designated and 26 non-designated) have been assessed by score-card marks for visual conditions, facilities, equipment, and methods. Over a period of one year fortnightly samples from these farms were subjected to routine resazurin tests and laboratory pasteurized counts. The results were compared with the total score-card marks and the equipment assessments of the farms. It was found that neither test alone sufficed to detect unsatisfactory production, but failure on the two tests combined agreed well with the production conditions and facilities.
The relation of season and mean shade atmospheric temperature to the thermoduric bacterial content of the milk was studied but no clear association was observed.     

Characterization of photodamage to escherichia coli in optical traps

Optical tweezers (infrared laser-based optical traps) have emerged as a powerful tool in molecular and cell biology. However, their usefulness has been limited, particularly in vivo, by the potential for damage to specimens resulting from the trapping laser. Relatively little is known about the origin of this phenomenon. Here we employed a wavelength-tunable optical trap in which the microscope objective transmission was fully characterized throughout the near infrared, in conjunction with a sensitive, rotating bacterial cell assay. Single cells of Escherichia coli were tethered to a glass coverslip by means of a single flagellum: such cells rotate at rates proportional to their transmembrane proton potential (. J. Mol. Biol. 138:541-561). Monitoring the rotation rates of cells subjected to laser illumination permits a rapid and quantitative measure of their metabolic state. Employing this assay, we characterized photodamage throughout the near-infrared region favored for optical trapping (790-1064 nm). The action spectrum for photodamage exhibits minima at 830 and 970 nm, and maxima at 870 and 930 nm. Damage was reduced to background levels under anaerobic conditions, implicating oxygen in the photodamage pathway. The intensity dependence for photodamage was linear, supporting a single-photon process. These findings may help guide the selection of lasers and experimental protocols best suited for optical trapping work.