Experimental apparatus for selection of adherent microorganisms under stringent growth conditions.

A bioreactor apparatus is described for studying bacterial attachment. A cyclic, on-off, flow regime was imposed within the apparatus. Model calculations illustrate the utility of this flow pattern in the selection and maintenance of slow-growing, adherent organisms. The apparatus is believed to have general utility in testing bacterial attachment influenced by many types of experimental or environmental constraints, including variations in fluid dynamics, presence of toxic substances (metals or organics), nature of the substratum surface, concentrations of limiting nutrients, and competition between bacterial strains. As an example application, the apparatus was employed to test 14 bacterial strains for surface attachment in a nutrient-limited growth medium. The medium was developed, using the chemical equilibrium program MINEQL, for planned studies of biofilms in a solution with a chemically defined composition that permits calculation of trace metal speciation. The apparatus was used to select organisms with growth and attachment characteristics that could not be evaluated by conventional batch, or chemostat, culture conditions. When supplied with acetate, pyruvate, or succinate as a carbon and energy source, the gram-negative strains Pseudomonas cepacia 17616 and Zoogloea sp. WGO4 showed superior attachment characteristics to glass surfaces in the chemically defined medium but only moderate fluid-phase growth. The gram-positive Arthrobacter sp. strain 9G4D and gram-negative species P. pickettii and Zoogloea sp. WNJ8, when supplied with pyruvate as a carbon and energy source, were capable of superior growth in the fluid phase but formed only a low to moderate biofilm surface coverage.     

Environmental control of ovarian dormancy in natural populations of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Drosophila melanogaster from Australia, Europe and North America enter an adult ovarian dormancy in response to short days and low temperatures. The independent effects of temperature and day length in the determination of dormancy have been examined only in one long-established laboratory line (Canton-S). In all other studies of natural or laboratory populations, dormancy has been assessed at either a single short day or a single moderately low temperature. Herein, we determine the relative roles of temperature, photoperiod, and their interaction in the control of ovarian dormancy in D. melanogaster from two natural populations representing latitudinal extremes in eastern North America (Florida at 27°N and Maine at 44°N). In both natural populations, temperature is the main determinant of dormancy, alone explaining 67% of the total variation among replicate isofemale lines, whereas photoperiod has no significant effect. We conclude that ovarian dormancy in D. melanogaster is a temperature-initiated syndrome of winter-tolerant traits that represents an adaptive phenotypic plasticity in temperate seasonal environments.     

Small mammals respond to extreme habitat fragmentation in the Brazilian Atlantic Forest according to the landscape continuum model

Mammal Research - There are several factors that can determine the pattern of habitat use by species in fragmented habitats. Here we investigated the applicability of the continuum model, which...     

Strategy maps: Generalised giving-up densities for optimal foraging

Finding a common currency for benefits and hazards is a major challenge in optimal foraging theory, often requiring complex computational methods. We present a new analytic approach that builds on the Marginal Value Theorem and giving-up densities while incorporating the nonlinear effect of predation risk. We map the space of all possible environments into strategy regions, each corresponding to a discrete optimal strategy. This provides a generalised quantitative measure of the trade-off between foraging rewards and hazards. This extends a classic optimal diet choice rule-of-thumb to incorporate the hazard of waiting for better resources to appear. We compare the dynamics of optimal decision-making for three foraging life-history strategies: One in which fitness accrues instantly, and two with delays before fitness benefit is accrued. Foragers with delayed-benefit strategies are more sensitive to predation risk than resource quality, as they stand to lose more fitness from a predation event than instant-accrual foragers.     

THE EFFECT OF CERTAIN RESPIRATORY INHIBITORS ON THE RESPIRATION OF CHLORELLA

Chlorella, when made heterotrophic by means of certain sugars, respires like other heterotrophic cells when subjected to the respiratory inhibitors, hydrocyanic acid, hydrogen sulfide, and carbon monoxide. Whether the case of Chlorella is typical for green cells in general remains to be seen. Experiments with various other green organisms are being carried out, in hope of settling this point.     

MEDICAL CARE AND PUBLIC HEALTH SERVICES

Medical care applies to the individual, and public health to the community. One is the concentrated application of diagnosis and treatment for the life, the comfort of a patient, and includes guidance in health as for motherhood, infancy, childhood and old age.Public health services, provided by the community through its local government and the local department of health, are concerned with the prevention of diseases of all kinds. Some are controlled by sanitary authority, but the majority of preventable diseases are dealt with by public health education.It is not the function of the health department to treat the sick. The family physicians, the hospitals and dispensaries provide for medical care. Medical care of the sick and public health protection are two parallel activities to make use of medical science, one for treatment, the other for prevention of disease.