Manoucher Shahamat

Cellulomonas persica sp. nov. and Cellulomonas iranensis sp. nov., mesophilic cellulose-degrading bacteria isolated from forest soils.

Two newly described species of mesophilic, cellulose-degrading, aerobic bacteria were isolated from forest humus soils along the southern border of the Caspian Sea. Cellulomonas persica and Cellulomonas iranensis are proposed as new specific epithets based on comparative sequence analyses of 16S rDNA, DNA-DNA hybridization and phenotypic characteristics. Formal species descriptions are provided.

Effects of selected physical and chemical parameters on uranium uptake by the bacterium Chryseomonas MGF-48

The effect of selected physical and chemical parameters, including media composition, uranium concentration, and metabolic inhibitors, on uranium uptake from aqueous solution by Chryseomonas sp. MGF-48, a bacterium isolated from electroplating effluent, was analysed. It was found that 198 mg/g (dry weight) of uranium was taken up from a 150 ppm (mg/l) solution of uranium when cells were maintained under starvation conditions. Uranium was released from the cells by addition of sodium carbonate. Uptake of uranium was reduced when cells were subjected to pretreatment with ultraviolet (u.v.) light (263.7 nm, 10 min) or heat (100 °C, 15 min), i.e., 99.8 and 57.5 mg/g, respectively. Addition of 2, 4-dinitrophenol (10 mM) or sodium azide (0.1%) resulted in decreased uptake (129 and 123 mg/g, respectively), whereas addition of glycerol-2-phosphate (G-2-P) resulted in deposition of uranium. Maximum uptake of uranium occurred at pH 6.5. Uranium uptake in the presence of selected carbohydrates decreased as follows: xylose > arabinose > mannose > maltose > glucose. When Chryseomonas sp. MGF-48 was exposed to 5, 50, or 100 mg/l uranium prior to uptake experiments, a decrease in uranium uptake was noted. Furthermore, immobilization of the bacterial cells in a calcium-alginate medium reduced the efficiency of uptake, yielding only 60% uranium uptake. It is concluded that uranium uptake and accumulation by this bacterium involves both metabolism-independent absorption and metabolism-dependent absorption, the former being considered to be more efficient.

Evaluation of media for recovery of aerosolized bacteria

Disease transmission by airborne bacteria is well known. Bacterial burden in indoor air is estimated by sampling the air and estimating Colony Forming Units (CFU) using a variety of media. In this study, the recovery of bacteria, after aerosolization in an aerosol chamber, and employing a variety of media, was compared to that achieved using Tryptic Soy Agar medium. The total number of cells present was determined by direct microscopy. All trials were conducted at approximately the same relative humidity (RH) and temperature using the same collection device. Twelve species of bacteria were tested and a total of 120 media or media combinations were evaluated. Recovery on 64 media formulations was significantly lower for all strains examined, and therefore, excluded from further consideration for the purposes of this study. Data for 56 of the media are presented. Three species (Bacillus subtilis, Staphylococcus aureus andSerratia marcescens) were selected as representative for reporting and testing recovery success. It is concluded that, for the media included in the study, there are large differences in recovery and successful recovery is related both to the effect of aerosolization and the type of medium employed for recovery. Brain Heart Infusion Agar (with horse serum), Tryptic Soy Agar and Mueller Hinton Agar yielded the best recoveries of aerosolized cultures. The most important finding was that only a small fraction of the airborne bacterial populations, enumerated by direct microscopy, could be recovered on any of the media tested, suggesting that culturable bacterial count is not a satisfactory means of estimating air microbial pollution.

Design, construction, and evaluation of a chamber for aerobiology

A chamber was designed and constructed for aeromicrobiology applications. An ultraviolet (UV) radiation source was incorporated to sterilize the chamber between trials. Twelve bacterial species originally isolated from air samples and obtained from the American Type Culture Collection were tested for efficacy of UV radiation disinfection of the chamber, comprising five Gram-positive bacteria, six Gram-negative and one Gram-variable bacterial species. Experiments were designed to determine time needed to sterilize the chamber walls and air within the chamber after an aerosol containing ≤108 bacteria/1 of air was introduced or suspensions of the microorganisms were placed on surfaces within the chamber. Exposure of surfaces to UV for 120 min was determined to provide sufficient disinfection for reuse of the chamber for aerobiology studies.

Prevalence of Pseudomonas aeruginosa pyocin and antibiotic biotypes in four Tehran hospitals

Over a 15‐month period, 340 strains of Pseudomonas aeruginosa were isolated from clinical specimens, i.e. sputum, wound swabs, pus, burns, urine, stool, etc., and the environment, i.e. sink, floor, bed sheets, etc., in four Tehran hospitals. Identification of Pseudomonas aeruginosa was carried out by standard methods. Pyocin typing and subtyping were done using the spotting method of Govan, and using a set of 13 indicator strains. Results of the study showed that the dominant pyocin types were PT10, PT4 and PT3, with frequencies of 30.6%, 21.7% and 8.8%, respectively. The pyocins had a wide spectrum of activity, in contrast to most other bacteriocins known. The dominant pyocin subtypes observed in this study were b, d, a, and c, with frequencies of 18.4%, 14.9%, 12.7%, 9.2%, respectively. Approximately 95.9% of the isolates were typable. 98.8% of the Pseudomonas aeruginosa isolates were resistant to 1 or more antibiotics tested. Antibiotic sensitivity tests were performed using the disc diffusion method, ...