No abstract

Evidence is brought for the presence of low molecular weight, heat stable, mercury reducing factors in Chlorella cells. Some of the properties of these factors, which appears to be normal metabolities, are described. These factors are also present in the medium in which the cells grow. The reduced mercury, Hg0, is volatilized from the culture medium more rapidly than Hg+2. The resultant decrease in the Hg concentration appears to be the main reason for the recovery of the cells from Hg stress. No resistance to Hg developed in cells emerging from the stress.

The rate of volatilization of Hg2+ as metallic Hg is accelerated by illumination of Chlorella cells. In the presence of the uncoupler methylamine the rate of volatilization in the light is greatly but transiently increased. DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea) prevented the light response. In the presence of Hg2+, O2 evolution by the cells was not completely inhibited by DCMU. Hg2+ appears to prevent DCMU reaching its binding site. Light seems to increase the amount of or leakage from the cells of a metabolite capable of reducing Hg2+ to Hg°.

The presence of Chlorella cells in a medium containing HgCl2 causes a rapid decrease of the mercury content in the algal suspension. The rate of decrease depends on the inoculum concentration. The presence of Hg in the medium induces a lag in the growth, whose length depends on the initial concentration of Hg and of theinoculum.Bindingand/oruptakeof mercury by thecelis is not dependent on temperature. The mercury content per cell declines somewhat at the time at which the culture resumes growth at a rate similar to that of the controls without mercury.

Treatment with aqueous toluene-ethanol has been shown to induce "pore" formation in plant cell membranes. The evidence i as folows: Althoug the phenomenon of pore induction is qultatively simlar to that in microorganisms, the pores induced appear to be smaler. It is proposed that induced leakage could be the bas for the development of simple and rapid methods for plant biochemial studies.Biochemical studies of cells provided with hard outer walls are hindered by the technical difficulties involved in homogenization. In the case of microorganisms a way of bypassing these difficulties has been developed. The formation of small holes is induced in the cell membrane by suitable techniques, the simplest being treatment with toluene (2, 5-7, 10, 12, 14-16, 19, 20 Preloading of the cytoplasm with fluorescein was achieved by incubating the roots for 10 min at room temperature in a 10 mm solution of KH2PO4 containing 1 mg of fluorescein/10 ml.Loading with ANS2 was achieved by incubating the roots for 10 min at room temperature in a 50 gM solution of ANS brought to pH 6 by addition of dilute NaOH containing 1% toluene and 4% ethanol.Cytoplasmic fluorescence induced by either fluorescein or ANS was observed with a Leitz Ortholux fluorescence microscope using transmission filters BG38 (4 mm) plus BG12 (3 mm) and suppression filter K530. Preloading of the vacuoles with neutral red was achieved by incubating the roots in an aqueous solution of the dye (1 mg/10 ml). Potassium phosphate buffer (pH 7.5) was then added to a final concentration of 10 mm and incubation continued for 1 hr. Although neutral red precipitates at this pH, the non-ionized species which is formed is lipid-soluble and penetrates the cellular membranes. After incubation the roots were rinsed several times in distilled H20.The procedure for compartment analysis was essentially similar to that described by Glinka (3). Course of influx of '4C-thiourea into Atriplex root at room temperature was found to be considerably faster than into carrot root. After 1 hr the labeled thiourea had reached equilibrium with the tissue. Atriplex roots were therefore loaded by incubation in 50 mm 14C-thiourea for 1 hr at room temperature. Efflux was measured by transferring the roots, in a holder, sequentially through a series of vials containing 6 ml of 50 mm nonradioactive thiourea. The vials were shaken constantly and were maintained at 4 C to slow down the process. During the first 2 min the roots were transferred every 15 sec to wash off the radioactivity adhering to the holder and to the surface of the roots. Subsequent efflux periods were progressively longer and continued for 3 hr.