Ameliorative effects of endogenous and exogenous indole-3-acetic acid on atrazine stressed paddy field cyanobacterial biofertilizer Cylindrospermum stagnale.

Across the world, paddy fields naturally harbour cyanobacteria that function as biofertilizers and secrete various compounds like Indole-3-acetic acid (IAA) that help organisms in regulating their growth. Also, paddy field farming utilizes large amounts of pesticides (e.g. atrazine); but their continued application in the agricultural field causes toxicity in non-target cyanobacterial species that hinder their performance as a biofertilizer. Hence, the current study is an attempt to ameliorate the atrazine stress in cyanobacterium Cylindrospermum stagnale by addition of IAA (1 mM each) under different atrazine levels (0, 60, 80, 100, 120, 140 µg/l). Atrazine toxicity affected C. stagnale in a dose-dependent manner further experiments revealed that both the exogenous and endogenous IAA mitigated the detrimental effects of atrazine. It reduced MDA content and simultaneously increased chlorophyll content, total protein content, and multiple antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] at 140 µg/l. A molecular docking study revealed that the pesticide binds to the D1 protein of the photoelectric chain in photosynthesis. Hence, the application of IAA or cyanobacterial biofertilizer that secretes a sufficient amount of IAA may assist sustainable agriculture in counteracting the atrazine toxicity.

Antibiofilm Activities of Biogenic Silver Nanoparticles Against Candida albicans.

Biofilms are microbial colonies that are encased in an organic polymeric matrix and are resistant to antimicrobial treatments. Biofilms can adhere to both biotic and abiotic surfaces, allowing them to colonize medical equipment such as urinary and intravenous catheters, mechanical heart valves, endotracheal tubes, and prosthetic joints. Candida albicans biofilm is the major etiological cause of the pathogenesis of candidiasis in which its unobstructed growth occurs in the oral cavity; trachea, and catheters that progress to systemic infections in the worst scenarios. There is an urgent need to discover novel biofilm preventive and curative agents. In the present investigation, an effort is made to observe the role of cyanobacteria-derived AgNPs as a new antibiofilm agent with special reference to candidiasis. AgNPs synthesized through the green route using Anabaena variabilis cell extract were characterized by UV-visible spectroscopy. The nanoparticles were spherical in shape with 11-15 nm size and were monodispersed. The minimum inhibitory concentration (MIC) of AgNPs was obtained at 12.5 µg/mL against C. albicans. AgNPs 25 µg/mL showed 79% fungal cell membrane permeability and 22.2% ROS production. AgNPs (25 µg/mL) also facilitated 62.5% of biofilm inhibition and degradation. Therefore, AgNPs could be considered as a promising antifungal agent to control biofilm produced by C. albicans.

Exogenous osmolytes suppresses the toxic effects of malathion on Anabaena variabilis.

Role of osmolytes is though well established for salt, drought and chilling stress, but their role in pesticide stress is yet to be explored thoroughly. The sporadic information covers our previous studies on proline with respect to endosulfan and carbaryl pesticides in cyanobacteria. Therefore, during the present investigation importance of osmolytes (exogenous and endogenous) is studied in cyanobacterial biofertilizer Anabaena variabilis in the presence of 25, 50, 75 and 100 µg mL(-1) malathion pesticide. Present investigation has two parts. In the first part we showed that malathion exert its toxic effect on growth (biomass) via. malondialdehyde (MDA) and hydrogen peroxide (H2O2). This was associated with quantitative enhancement of endogenous osmolytes (proline, sucrose, mannitol, trehalose and glycogen). In the second part effort was made to corelate effect of exogenous addition of osmolytes (which were detected in the first part of this study) on growth and antioxidant enzymes [like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] of A. variabilis in the presence of 100 µg mL(-1) malathion. Surprisingly it was observed that exogenous osmolytes gave additional protection to the organism. The order of protection provided by osmolytes was as trehalose>glycogen>sucrose>mannitol>proline in A. variabilis.

Chromium (VI) induced oxidative stress in Hapalosiphon fontinalis.

Heavy metals in air, soil, and water are great threat to the environment. Effluents from paint, tannery, electroplating industries contaminate irrigation water, which in turn exhibit toxic response to many crops and microorganisms including cyanobacterial biofertilizers. In aquatic system Cr exist in many forms, whereas, Cr(VI) is most toxic. In the present study metabolic alteration were studied in a cyanobacterial biofertilizer (Hapalosiphon fontinalis) in response to chromium (VI) with special reference to oxidative stress. Maximum growth inhibition was observed at 0.5 mM Cr at 20th day. Lipid peroxidation as TBARS increased with the increase in chromium concentration and suggested free radical mediated toxicity. Elevated levels of ß- carotene, astaxanthin, superoxide dismutase, catalase and ascorbate peroxidase indicated their role in survival strategy of the test organism.