Microbial pectinolytic enzymes: A review

Extracellular polymeric substances (EPS) produced by microorganisms are a complex mixture of biopolymers primarily consisting of polysaccharides, as well as proteins, nucleic acids, lipids and humic substances. EPS make up the intercellular space of microbial aggregates and form the structure and architecture of the biofilm matrix. The key functions of EPS comprise the mediation of the initial attachment of cells to different substrata and protection against environmental stress and dehydration. The aim of this review is to present a summary of the current status of the research into the role of EPS in bacterial attachment followed by biofilm formation. The latter has a profound impact on an array of biomedical, biotechnology and industrial fields including pharmaceutical and surgical applications, food engineering, bioremediation and biohydrometallurgy. The diverse structural variations of EPS produced by bacteria of different taxonomic lineages, together with examples of biotechnological applications, are discussed. Finally, a range of novel techniques that can be used in studies involving biofilm-specific polysaccharides is discussed.

https://www.mdpi.com/1420-3049/14/7/2535/pdf

Bacterial extracellular polysaccharides involved in biofilm formation.

https://www.cell.com/trends/neurosciences/pdf/S0166-2236(08)00163-X.pdf

Neuronal calcium mishandling and the pathogenesis of Alzheimer's disease.

Phosphatidylserine (PS) is the most abundant negatively charged phospholipid in eukaryotic membranes. PS directs the binding of proteins that bear C2 or gamma-carboxyglutamic domains and contributes to the electrostatic association of polycationic ligands with cellular membranes. Rather than being evenly distributed, PS is found preferentially in the inner leaflet of the plasma membrane and in endocytic membranes. The loss of PS asymmetry is an early indicator of apoptosis and serves as a signal to initiate blood clotting. This review discusses the determinants and functional implications of the subcellular distribution and membrane topology of PS.

The distribution and function of phosphatidylserine in cellular membranes.

Autoimmunity and the Clearance of Dead Cells

Pseudomonas sp. isolated from soil of coffee plantation area has been shown to degrade higher concentrations of caffeine (∼15 g l–1) by N-demethylation at a rate higher than what has been reported for any strain so far. This strain exhibits positive chemotaxis towards caffeine (1,3,7-trimethylxanthine) in swarm plate assay and modified capillary assay in a dose dependant manner. Related methylxanthines and xanthine also act as chemoattractants for the strain with the highest relative chemotactic response (RCR) seen for xanthine. Chemotaxis in Pseudomonas sp. is possibly plasmid mediated as indicated by positive chemotaxis of plasmid transformed E. coli DH5α. The chemotactic abilities of Pseudomonas sp. combined with higher rates of degradation of caffeine can be used in the development of strategies for biodecaffeination of caffeine containing wastes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Chemotaxis of Pseudomonas sp. to caffeine and related methylxanthines.

The effect of salt, pH, and temperature stress on the cellular level of antioxidant enzymes, catalase and superoxide dismutase (SOD) and glycerol-3-phosphate dehydrogenase (G3PDH) was studied in Debaryomyces nepalensis NCYC 3413, a halotolerant yeast. The catalase activity increased in different phases, while SOD and G3PDH activities declined in late stationary phase. A significant increase in SOD activity was observed under different stress as compared to control. Salt and temperature stress enhanced the catalase activity where as it was suppressed by pH stress. G3PDH level increased with salt stress, however, no significant change was observed under pH and temperature stress. The observations recorded in this investigation suggested that D. nepalensis has an efficient protective mechanism of antioxidant enzymes and G3PDH against salt, pH, and temperature stresses.

Differential response of the catalase, superoxide dismutase and glycerol-3-phosphate dehydrogenase to different environmental stresses in Debaryomyces nepalensis NCYC 3413

Cyclic glucans are predominantly produced by Agrobacterium, Bradyrhizobium, and Rhizobium sp. They are more water soluble and biocompatible than cyclodextrin, and are produced from renewable resources. Glucans are linked by either a or b glycosidic bonds and are either linear or branched. They are food reserve material in bacteria and their concentrations in Rhizobiaceae are as high as 20 % of the total cell dry weight. They occur as storage polysaccharides in eukaryotes. Derivatives of cyclic a-glucans are mainly isolated from amylose by cyclodextrin glucanotransferase. Curdlan, the linear glucan, is found both in prokaryotes and eukaryotes.

Cyclic β-Glucans from Microorganisms

Effect of cosubstrate on xylitol production by Debaryomyces nepalensis NCYC 3413: A cybernetic modelling approach

To isolate cyclic (1 → 3, 1 → 6)-β-glucan from Bradyrhizobium japonicum MTCC120, to characterize its structure and to study its biological activities. The degree of polymerization of cyclic (1 → 3, 1 → 6)-β-glucan varied between 10 and 13 and with substituents acetyl, succinyl and phosphocholine. The cyclic glucans showed bimodal particle size distribution, with hydrodynamic diameters of 1.92 and 231 nm corresponding to monomeric and aggregated cyclic glucans, respectively. SEM and TEM images showed that the glucans formed aggregates of nanorods. The glucans were biocompatible, exhibited good antioxidant activity and had the abilities to bind to Aniline Blue dye to form a fluorescence complex which was concentration dependent. The glucans isolated are cyclic and have good antioxidant activities, hence have potential application in food and pharmaceutical industries. Their dye binding ability could be exploited in medical imaging to reduce the cytotoxicity of the dyes.

Sathyanarayana N. Gummadi

Papers

Chemotaxis of Pseudomonas sp. to caffeine and related methylxanthines.

Differential response of the catalase, superoxide dismutase and glycerol-3-phosphate dehydrogenase to different environmental stresses in Debaryomyces nepalensis NCYC 3413

Cyclic β-Glucans from Microorganisms

Effect of cosubstrate on xylitol production by Debaryomyces nepalensis NCYC 3413: A cybernetic modelling approach

Characterization and biological activities of cyclic (1 → 3, 1 → 6)-β-glucans from Bradyrhizobium japonicum