Aamir Ghafoor

Bio: Aamir Ghafoor is an academic researcher from University of Veterinary and Animal Sciences. The author has contributed to research in topics: Materials science & Dielectric. The author has an hindex of 11, co-authored 33 publications receiving 839 citations. Previous affiliations of Aamir Ghafoor include Massey University.

Role of exopolysaccharides in Pseudomonas aeruginosa biofilm formation and architecture

Abstract: Pseudomonas aeruginosa is an opportunistic human pathogen and has been established as a model organism to study bacterial biofilm formation. At least three exopolysaccharides (alginate, Psl, and Pel) contribute to the formation of biofilms in this organism. Here mutants deficient in the production of one or more of these polysaccharides were generated to investigate how these polymers interactively contribute to biofilm formation. Confocal laser scanning microscopy of biofilms formed in flow chambers showed that mutants deficient in alginate biosynthesis developed biofilms with a decreased proportion of viable cells than alginate-producing strains, indicating a role of alginate in viability of cells in biofilms. Alginate-deficient mutants showed enhanced extracellular DNA (eDNA)-containing surface structures impacting the biofilm architecture. PAO1 ΔpslA Δalg8 overproduced Pel, and eDNA showing meshwork-like structures presumably based on an interaction between both polymers were observed. The formation of characteristic mushroom-like structures required both Psl and alginate, whereas Pel appeared to play a role in biofilm cell density and/or the compactness of the biofilm. Mutants producing only alginate, i.e., mutants deficient in both Psl and Pel production, lost their ability to form biofilms. A lack of Psl enhanced the production of Pel, and the absence of Pel enhanced the production of alginate. The function of Psl in attachment was independent of alginate and Pel. A 30% decrease in Psl promoter activity in the alginate-overproducing MucA-negative mutant PDO300 suggested inverse regulation of both biosynthesis operons. Overall, this study demonstrated that the various exopolysaccharides and eDNA interactively contribute to the biofilm architecture of P. aeruginosa.

Bacterial biosynthesis of alginates

Abstract: Alginates are polysaccharides with many industrial and medical uses, from food additives to encapsulation agents in the emerging transplantation technologies. Alginate is composed of variable proportions of ! -D-mannuronic acid and " -Lguluronic acid linked by 1‐4 glycosidic bonds. Traditionally, commercial alginate has been produced by farmed brown seaweeds, but this alginate suffers from heterogeneity in composition and quality partly due to environmental variation. Two bacterial genera, Pseudomonas and Azotobacter, are also capable of producing alginate as an exopolysaccharide. These bacterial alginate producers can provide the means to produce alginates with defined monomer composition and possibly through genetic and protein engineeringmayallow for the production of ‘tailor made’bacterial alginates.The paper discusses the mechanismsbehind alginate production in bacteria and howtheymaybeusedin thecommercialpro ductionofalginat es. c ! 2010 Society of Chemical Industry

Nanotoxicity of Inert Materials: The Case of Gold, Silver and Iron.

Abstract: Nanotechnology has opened a new horizon of research in various fields including applied physics, chemistry, electronics, optics, robotics, biotechnology and medicine. In the biomedical field, nanomaterials have shown remarkable potential as theranostic agents. Materials which are considered inert are often used in nanomedicine owning to their nontoxic profile. At nanoscale, these inert materials have shown unique properties that differ from bulk and dissolved counterparts. In the case of metals, this unique behavior not only imparts paramount advantages but also confers toxicity due to their unwanted interaction with different cellular processes. In the literature, the toxicity of nanoparticles made from inert materials has been investigated and many of these have revealed toxic potential under specific conditions. The surge to understand underlying mechanism of toxicity has increased and different means have been employed to overcome toxicity problems associated with these agents. In this review, we have focused nanoparticles of three inert metallic materials i.e. gold, silver and iron as these are regarded as biologically inert in the bulk and dissolved form. These materials have gained wider research interest and studies indicating the toxicity of these materials are also emerging. Oxidative stress, physical binding and interference with intracellular signaling are the major role player in nanotoxicity and their predominance is highly dependent upon size, surface coating and administered dose of nanoparticles. Current strategies to overcome toxicity have also been reviewed in the light of recent literature. The authors also suggested that uniform testing standards and well-designed studies are needed to evaluate nanotoxicity of these materials that are otherwise considered as inert. This article is open to POST-PUBLICATION REVIEW . Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Genetic diversity of Newcastle disease virus in Pakistan: a countrywide perspective

Abstract: Newcastle disease (ND) is one of the most deadly diseases of poultry around the globe. The disease is endemic in Pakistan and recurrent outbreaks are being reported regularly in wild captive, rural and commercial poultry flocks. Though, efforts have been made to characterize the causative agent in some of parts of the country, the genetic nature of strains circulating throughout Pakistan is currently lacking. To ascertain the genetics of NDV, 452 blood samples were collected from 113 flocks, originating from all the provinces of Pakistan, showing high mortality (30–80%). The samples represented domesticated poultry (broiler, layer and rural) as well as wild captive birds (pigeons, turkeys, pheasants and peacock). Samples were screened with real-time PCR for both matrix and fusion genes (1792 bp), positive samples were subjected to amplification of full fusion gene and subsequent sequencing and phylogenetic analysis. The deduced amino acid sequence of the fusion protein cleavage site indicated the presence of motif (112RK/RQRR↓F117) typical for velogenic strains of NDV. Phylogenetic analysis of hypervariable region of the fusion gene indicated that all the isolates belong to lineage 5 of NDV except isolates collected from Khyber Pakhtunkhwa (KPK) province. A higher resolution of the phylogenetic analysis of lineage 5 showed the distribution of Pakistani NDV strains to 5b. However, the isolates from KPK belonged to lineage 4c; the first report of such lineage from this province. Taken together, data indicated the prevalence of multiple lineages of NDV in different poultry population including wild captive birds. Such understanding is crucial to underpin the nature of circulating strains of NDV, their potential for interspecies transmission and disease diagnosis and control strategies.

Pseudomonas aeruginosa Lifestyle: A Paradigm for Adaptation, Survival, and Persistence.

Abstract: Pseudomonas aeruginosa is an opportunistic pathogen affecting immunocompromised patients. It is known as the leading cause of morbidity and mortality in cystic fibrosis (CF) patients and as one of the leading causes of nosocomial infections. Due to a range of mechanisms for adaptation, survival and resistance to multiple classes of antibiotics, infections by P. aeruginosa strains can be life-threatening and it is emerging worldwide as public health threat. This review highlights the diversity of mechanisms by which P. aeruginosa promotes its survival and persistence in various environments and particularly at different stages of pathogenesis. We will review the importance and complexity of regulatory networks and genotypic-phenotypic variations known as adaptive radiation by which P. aeruginosa adjusts physiological processes for adaptation and survival in response to environmental cues and stresses. Accordingly, we will review the central regulatory role of quorum sensing and signaling systems by nucleotide-based second messengers resulting in different lifestyles of P. aeruginosa. Furthermore, various regulatory proteins will be discussed which form a plethora of controlling systems acting at transcriptional level for timely expression of genes enabling rapid responses to external stimuli and unfavorable conditions. Antibiotic resistance is a natural trait for P. aeruginosa and multiple mechanisms underlying different forms of antibiotic resistance will be discussed here. The importance of each mechanism in conferring resistance to various antipseudomonal antibiotics and their prevalence in clinical strains will be described. The underlying principles for acquiring resistance leading pan-drug resistant strains will be summarized. A future outlook emphasizes the need for collaborative international multidisciplinary efforts to translate current knowledge into strategies to prevent and treat P. aeruginosa infections while reducing the rate of antibiotic resistance and avoiding the spreading of resistant strains.