Purpurin suppresses Candida albicans biofilm formation and hyphal development

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Pseudomonas aeruginosa inhibits in-vitro Candida biofilm development

<p>Abstract</p> <p>Background</p> <p>Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as <it>Candida spp</it>. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of <it>Pseudomonas aeruginosa </it>and six different species of <it>Candida </it>comprising <it>C. albicans</it>, <it>C. glabrata, C. krusei</it>, <it>C. tropicalis</it>, <it>C. parapsilosis</it>, and <it>C. dubliniensis </it>in dual species biofilm development.</p> <p>Results</p> <p>A significant reduction in colony forming units (CFU) of <it>C. parapsilosis </it>(90 min), <it>C. albicans </it>and <it>C. tropicalis </it>(90 min, 24 h and 48 h), <it>C. dubliniensis </it>and <it>C. glabrata</it>, (24 h and 48 h) was noted when co-cultured with <it>P. aeruginosa </it>in comparison to their monospecies counterparts (P < 0.05). A simultaneous significant reduction in <it>P. aeruginosa </it>numbers grown with <it>C. albicans </it>(90 min and 48 h), <it>C. krusei </it>(90 min, 24 h and 48 h),<it>C. glabrata</it>, (24 h and 48 h), and an elevation of <it>P. aeruginosa </it>numbers co-cultured with <it>C. tropicalis </it>(48 h) was noted (P < 0.05). When data from all <it>Candida spp</it>. and <it>P. aeruginosa </it>were pooled, highly significant mutual inhibition of biofilm formation was noted (<it>Candida </it>P < 0.001, <it>P. aeruginosa </it>P < 0.01). Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) analyses confirmed scanty architecture in dual species biofilm in spite of dense colonization in monospecies counterparts.</p> <p>Conclusions</p> <p><it>P. aeruginosa </it>and <it>Candida </it>in a dual species environment mutually suppress biofilm development, both quantitatively and qualitatively. These findings provide a foundation to clarify the molecular basis of bacterial-fungal interactions, and to understand the pathobiology of mixed bacterial-fungal infections.</p

Microbial chemical signaling: a current perspective

Communication among microorganisms is mediated through quorum sensing. The latter is defined as cell-density linked, coordinated gene expression in microbial populations as a response to threshold signal concentrations followed by induction of a synchronized population response. This phenomenon is used by a variety of microbes to optimize their survival in a constantly challenging, dynamic milieu, by correlating individual cellular functions to community-based requirements. The synthesis, secretion, and perception of quorum-sensing molecules and their target response play a pivotal role in quorum sensing and are tightly controlled by complex, multilayered and interconnected signal transduction pathways that regulate diverse cellular functions. Quorum sensing exemplifies interactive social behavior innate to the microbial world that controls features such as, virulence, biofilm maturation, antibiotic resistance, swarming motility, and conjugal plasmid transfer. Over the past two decades, studies have been performed to rationalize bacterial cell-to-cell communication mediated by structurally and functionally diverse small molecules. This review describes the theoretical aspects of cellular and quorum-sensing mechanisms that affect microbial physiology and pathobiology. © 2012 Informa Healthcare USA, Inc.link_to_subscribed_fulltex

Bacterial lipopolysaccharide modifies Candida albicans biofilm development at transcriptional level

Session - Candida: abstract no. 3486OBJECTIVE: To evaluate the effect of Gram negative bacterial lipopolysaccharides (LPS) on C. albicans hyphal development and its transcriptional regulation during biofilm formation. METHODS: The effect of LPS from P. aeruginosa ATCC 27316 and K. pneumoniae ATCC 15380 on different C. albicans strains (ATCC 90028, SC 5314, and a clinical strain) were studied using a standard biofilm assay. Candida biofilms developed on polystyrene surfaces were treated with LPS at 90 min. The effect of LPS was assessed quantitatively by XTT reduction assay (XTT) at 48h, growth curve assay and light microscopy, and qualitatively, by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). RNA was extracted from both test and control C. albicans SC 5314 biofilms at 1h, 3h, 6h, 12h, 24h and 48h. Differential expression of hypha specific genes (HSGs); ECE1, HWP1, HYR1, RBT1, RBT4, ALS3 and ALS8 at 48h and the transcription factor EFG1 at all time points were evaluated with quantitative Real time PCR assay. Cyclic AMP levels of 48h test and control biofilms were quantified by cAMP competitive ELISA. RESULTS: XTT data showed significantly lower metabolic activities in LPS treated C. albicans SC 5314 and clinical strain biofilms (p<0.05). Growth curves exhibited constantly lower optical density in LPS treated biofilms. Light microscopy demonstrated higher proportions of budding yeasts (89%) in test biofilm compared to its control (73%). SEM and CLSM further confirmed these data. All HSGs in the test biofilm were significantly upregulated at 48h (p<0.05). EFG1 was significantly upregulated at all six time points (p<0.05). No significant difference was noted in cAMP concentration in control and test biofilms. Conclusion: Bacterial LPS acts downstream of EFG1 in cAMP/PKA signaling pathway in C. albicans and upregulates HSGs, with a paradoxical suppression of biofilm development possibly due to an increased production of budding yeasts. (Supported by CERG#HKU-7624/06M)link_to_OA_fulltextThe 89th General Session and Exhibition of IADR/AADR/CADR, San Diego, CA., 16-19 March 2011

Pseudomonas aeruginosa lipopolysaccharide enhances Candida albicans hypha specific gene expression

Introduction: Demystification of cellular interactions in mixed biofilms has a major impact on therapeutics. Objective: Evaluation of the effect of bacterial lipopolysaccharide (LPS) on Candida albicans biofilm formation and its hyphal development. Method: The effect Pseudomonas aeruginosa LPS on C. albicans SC 5314 was studied using a standard biofilm assay. Biofilm formation of LPS treated C. albicans on polystyrene surfaces was quantified at 90min, 24h and 48h by a XTT reduction assay. Biofilms were qualitatively and quantitatively analyzed using Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM). The effect of LPS on hypha specific genes (HSGs) of C. albicans was evaluated with quantitative Real time PCR. Farnesol, a natural pesticide, was also evaluated. Differential expression of HSGs; ECE1, HWP1, HYR1, RBT1, RBT4, ALS3 and ALS8 were assessed at 24h biofilms. Results: Adhesion of C. albicans (90 min) was significantly enhanced by P. aeruginosa LPS (P<0.05). CLSM and SEM further confirmed these data. All HSGs tested were significantly upregulated when treated with LPS and was significantly downregulated when treated with farnesol (p<0.05). Conclusion: P. aeruginosa LPS significantly enhances in vitro C. albicans hyphal development though it does not appear to affect the Candida biofilm metabolic activity