An experimental analysis of cache recovery in Clark's nutcracker

Five hypotheses of cache recovery behaviour in Clark's nutcracker (Nucifraga columbiana) were examined experimentally. Most caches were made in soil within 5 cm of conspicuous large objects. Both seed-caching and non-seed-caching nutcrackers were able to locate caches. Seed-caching nutcrackers relocated caches using large objects as remembered visual cues. Soil microtopography and small (<2 cm diameter) objects may be used as cues to facilitate cache recovery but are not essential. Non-seed-caching nutcrackers located caches by using soil disturbances at cache sites as visual cues and by searching preferentially near objects where caches were concentrated. Success rates of seed-caching nutcrackers ranged from 52 to 78% and those of non-seed-caching nutcrackers ranged from 8 to 12%. Nutcrackers do not use random search or olfactory cues to locate caches.     

Respiratory components in acidophilic bacteria that respire on iron

Abstract

Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state.

Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions     

A multiple chemostat system for consortia studies on microbially influenced corrosion

A multiple chemostat system has been developed in which metal specimens can be exposed to a consortium of bacteria. The system comprises a single test chemostat containing the test specimen operated at a high dilution rate to facilitate the wash out of planktonic bacteria, selecting for attached or biofilm growth. This chemostat is fed at a steady low rate by a number of separate chemostats each of which contains a pure axenic culture of one member of the consortium being tested. This system has the advantage of providing a continual inoculum of the test species to the test specimen allowing both aerobic and anaerobic bacteria to be grown in the same system. Constant levels of three bacterial types were maintained in the system: Pseudomonas aeruginosa, Thiobacillus ferrooxidans and Desulfovibrio vulgaris. Exposure of 316L stainless steel electrodes to this system resulted in increased corrosion of coupons exposed biotically, as compared to those exposed abiotically. A current monitoring technique and electrochemical impedance spectroscopy were used to evaluate effects of bacteria on metallic corrosion.     

Fluorometric, Chromatographic, and Spectronic Evidence for the Non-indolic Nature of Citrus Auxin

Evidence for the non-indolic nature of the new citrus auxinis presented on the basis of fluorometric properties, thin-layerchromatography, Ehrlich's colour reaction, paper electrophoresis,and the infra-red spectra determinations. Citrus auxin had alower Rf in TLC than IAA, did not give the typical indole reactionwith Ehrlich's reagent, and behaved differently in electrophoresis.The infra-red spectra also provided preliminary informationconcerning chemical structure. The hypothesis that indolic compoundsconstitute the only natural auxins in higher plants should berevised in view of this evidence that a non-indole auxin existsin higher plants.     

Preharvest aflatoxin contamination: effect of moisture and substrate variation in developing cottonseed and corn kernels.

Variations in moisture and substrate in preharvest corn kernels and cottonseed were linked with the ability of Aspergillus parasiticus to infect the seed and produce aflatoxin. Osmotic pressures and moisture content (MC) levels of developing starch-rich corn kernels and lipid-rich cottonseed were determined. For in vivo studies, corn kernels and cottonseed were inoculated with A. parasiticus conidia and retained on plants through maturation. For in vitro studies, samples of corn kernels and cottonseed were collected at various stages, sterilized, inoculated, incubated for 2 weeks, and assayed for toxin. Aflatoxin levels were highest in corn kernels inoculated at 28 days postflowering (52% MC) in both the in vivo and in vitro tests. Toxin concentrations in cottonseed were greatest with inoculation at 35 days postflowering (70% MC) in seed retained on the plant, but toxin accumulation continued to increase with the maturity of the seed inoculated in cottonseed used in the in vitro trials. Moisture and substrate conditions in the midrange of seed development provided optimum conditions for fungal development and toxin production in seed retained on the plant.