Rubina Arshad

Improvement of penicillin G acylase expression in Escherichia coli through UV induced mutations.

We used ultraviolet (UV) radiation to induce mutation in three locally isolated strains of Escherichia coli. Different dilutions of bacterial cultures were exposed to UV lamp of 254 nm wavelength for different time intervals at varied distances ranging from 5 to 210 sec and 5 to 100 cm. Viable colonies were screened for mutants with an increased production of penicillin G acylase (PGA) and a reduced production of β-lactamase, which are the desired properties of PGA producing industrial strains. A survival curve was made to get optimum exposure time and distance. The survival percentage for each exposure period was calculated and 1-5% survival was found useful for obtaining mutants with desired change. Screening for PGA and β-lactamase constitutive and/or deficient mutants was made by Serratia marcescens overlay test. A total of 100 survivors were selected of which 49% expressed PGA activity higher than the parent strain. Frequency of β-lactamase constitutive and deficient mutants was 48 and 52%, respectively. The best hyper-producing mutant (BDCS-N-M74), with almost negligible expression of β-lactamase, exhibited three-fold (22.5 mg 6-APA h-1 mg-1 wet cells) increase in PGA activity compared with that in the parent strain (6.7 mg 6-APA h-1 mg-1 wet cells). The results indicated the successful induction of UV mediated mutation in E. coli for PGA hyper-producing mutants lacking β-lactamase activity.

Mutagenic effect of acridine orange on the expression of penicillin G acylase and β-lactamase in Escherichia coli

Aims:  The present work aimed to improve the production of penicillin G acylase (PGA) and reduce the β‐lactamase activity through acridine orange (AO) induced mutation in Escherichia coli.

Practical, Productive, and Environment-Friendly Utilization of Different Categories of Salt-Affected Soils in Arid and Semiarid Regions of Pakistan

Saline soils in Pakistan are of three types. First type includes porous saline and saline-sodic soils (4.79 × 106 ha) located in irrigated areas. These soils possess electrical conductivity in the range of 10–15 dS m−1 and can be cultivated with salt-tolerant wheat. A short-duration and short-stature wheat line (SSt) was developed for such areas which is also resistant to lodging that may occur as a consequence of irrigation. The second types of soils (1.5 × 106 ha) have twin problems of salinity and water deficiency and are located in water-deficit areas of southern Punjab and parts of Sindh. A drought-tolerant wheat line (DTL) was developed for these areas which can be grown with only pre-sowing irrigation and can produce grain yield of about 6,000 kg ha−1. The third types of soils (11 × 106 ha) are located in Cholistan, Thar, Thal, and Kharan areas beset with salinity, high rate of evaporation, and strong winds. Water is most critical and limiting factor that prohibits agriculture production under such areas. Wheat variety “DURUGEN” was developed for these soils which combine tolerance for salt, water deficiency, and high temperature. It can be cultivated in desert areas for production of green biomass which can be used (1) as fodder to raise sheep and goats, (2) to provide green cover to barren lands thereby improving both land and the environment, and (3) to help providing livelihood to the poor natives. This chapter provides details of specific wheat genotypes and successful cultivation of these genotypes on saline soils.

Mapping of esterase loci in Aegilops uniaristata and homoeologous group 3 chromosomes of wheat

This study was planned to identify the chromosomal location of esterase loci in wheat (Triticum aestivum), in comparison to Aegilops uniaristata, using wheat Ae. uniaristata disomic addition and translocation lines. Two loci (Est-N1 and Est-N8) were identified on 3N chromosome of Ae. uniaristata and their probable homoeoloci were, for the first time, mapped close to three RFLP probes (Xpsr56, Xpsr394, and Xpsr1196) on homoeologous group 3 wheat chromosomes.