نشریه زیست شناسی کاربردی
سال بیست و پنجم شماره 2 (پاییز و زمستان 1391)

The aim of this work was to investigate Pseudomonas sp. as biosorbent, for the fixation of nickel ions in batch reactor. Pollution of the environment by toxic metals is a major environmental problem. In a first step, biosorption kinetics and isotherms have been performed at pH 5.0. The equilibrium time was about 5 min and the adsorption equilibrium data were well described by the Langmuir`s equation. The maximum capacity has been extrapolated to 6.44 mg.g-1. The release of nickel ions, from Pseudomonas sp. by desorption agent such as nitric acid, has been studied. Finally the effects of biomass form, effect of pH values, were studied. These results indicate that Pseudomonas sp. is an excellent candidate for use in reactor to remove nickel ions from polluted aqueous effluents.

Improvement of growth and development of potato plant under in vitro culture is important. Ethylene is one of the phytohormones accumulating in the culture vessel and decreases the potato growth and development. In this study, the effect of nanosilver on chlorophyll content, gibberellic acid and total protein and electrophoresis pattern of protein of treated plants in MS medium suplemented with nanosilver (0.5, 1, 1.5 and 2 ppm) after 5 weeks were evaluated. Chlorophyll content did not show any significant difference compared with the control plant. Total protein was increased with increasing of nanosilver concentrations. Electrophoresis pattern of proteins showed some changes in 3 protein bands compared with untreated plants.

Salix is one of the largest genera in Salicaceae family. In this research epidermis and leaf anatomical characters in six species of Salix from three sections were studied. The specimens were collected from Karadj (Alburz station). These characters were as follow: shape and patterns of anticlinal cells of lower epidermis, type, size and density of stomata, mesophyll type, the number of paliside layers and cell shape, type and distribution of crystals, number and shape of hypodermis cells. polygonal and irregular epidermis cells were found in four species and polygonal and regular cells in two species. There was several type of stomata in the species. All species had one layer of hypodermis, but the shape of the cells was variable in different species. Mesophylle type was isolateral and without space. The number of palisade layer and crystal distribution were variable in different species. The results showed that some of the anatomical characters were similar in six species. The shape of epidermis cells and anticlinal patterns was constant in each species. This constancy could separate some species.

Most of the infections caused by Staphylococcus aureus resistant strains are from hospital origin. The prevalence of these infections and antibiotic resistance among them is increasing in many countries. So, many efforts has been made to find the new compounds as a substitute for antibiotics. This study investigate the antibacterial effect of extract of Cayenne pepper, Amaranthus retroflexus and Satureja hortensis against antibiotic-resistant Staphylococcus aureus strains. Ethanolic extract of Cayenne pepper, Amaranthus retroflexus and Satureja hortensis were prepared. Their MIC, as well as MBC was determined against 17 strains of S. aureus isolated from nose and throat areas, using microtiter-plate method. Concordance was observed between the lower amonts of their extacts and lower inhibition. MIC for Cayenne pepper, Amaranthus retroflexus and Satureja hortensis were 11،5/25, 25// and 52/ mg/ml, while their MBC were 5, 10, and 10 mg/ml, respectively.

Haloarcula IRU1 is an extreme halophilic archaeon isolated from Uromia salt lake. This isolate shows high resistance to DNA damaging agents such as H2O2. This radioresistant organism contains red-orange pigments. In the present study, DNA strand breaks were produced by hydrogen peroxide in a Fenton reaction in the presence and absence of haloarchaeon carotenoid and β-carotene as a standard antioxidant. Carotenoids of Haloarcula IRU1 diminished significantly production of DNA strand breaks in comparison with β-carotene. We propose that radio-resistance of Haloarcula IRU1 is partially due to carotenoids which act as effective in vitro antioxidant.

A comparative study was carried out on the production of alkaline protease using wheat straw as substrate in solid-state fermentation (SSF) and submerged fermentation (SMF). A strain of bacillus. spp was isolated from Guilan alkaline soils and after screening for enzyme production enzyme activity was assayed in SSF and SmF simultaneously. The best result were obtain at 100% initial moisture content, 40% inoculums size, temperature 37◦c and initial PH 9.4 in SSF. In the same condition enzyme production in SSF (4025u/gr) was 1.9 fold of SmF (2100u/ml).

Xanthan, the extracellular polysaccharide of the phytopathogenic bacterium Xanthomonas campestris, has many applications in different industries, especially in petroleum, food and pharmaceutical industries. Development of the simple and inexpensive methods for accurate measurement of xanthan concentration in aqueous solutions would be greatly appreciated. In this work, quantitative effect of xanthan interaction with congo-red was spectrophotometrically evaluated. It was demonstrate that at low concentrations, xanthan, induces hypochromocity (decreasing of the maximum absorbance) in solutions of congo red dye. Also, an overnight conservation of xanthan solutions before performing the colorimetric test is recommended for its establishment; simple up/down agitation provides an appropriate and quick procedure to obtain a mixture of the colored liquid and the xanthan solution. The best results were obtained by using Congo red dye at 4080- μg/l concentrations, 492 nm wavelength at all of the tested xanthan concentrations. Heating of xanthan solutions at 121 °C affected the absorbance without remarkable change in pattern of absorbance. This research provides basic information for development of a colorimetric method for measurement of xanthan concentration in aqueous solutions.