Inhibition of Candida albicans morphogenesis by chitinase from Lactobacillus rhamnosus GG

Abstract Lactobacilli have been evaluated as probiotics against Candida infections in several clinical trials, but with variable results. Predicting and understanding the clinical efficacy of Lactobacillus strains is hampered by an overall lack of insights into their modes of action. In this study, we aimed to unravel molecular mechanisms underlying the inhibitory effects of lactobacilli on hyphal morphogenesis, which is a crucial step in C. albicans virulence. Based on a screening of different Lactobacillus strains, we found that the closely related taxa L. rhamnosus, L. casei and L. paracasei showed stronger activity against Candida hyphae formation compared to other Lactobacillus species tested. By exploring the activity of purified compounds and mutants of the model strain L. rhamnosus GG, the major peptidoglycan hydrolase Msp1, conserved in the three closely related taxa, was identified as a key effector molecule. We could show that this activity of Msp1 was due to its ability to break down chitin, the main polymer in the hyphal cell wall of C. albicans. This identification of a Lactobacillus-specific protein with chitinase activity having anti-hyphal activity will assist in better strain selection and improved application in future clinical trials for Lactobacillus-based Candida-management strategies

Investigating the Efficacy of Focused and Unfocused Corrective Feedback on the Accurate Use of Prepositions in Written Work

This paper discusses findings from a study investigating feedback efficacy on the accurate use of prepositions by ESL learners in written work over a period of 12 weeks. The study involved two treatment groups and a control group comparing the differential effects of the focused indirect with the unfocused indirect corrective feedback on the uptake and retention measured from the pretest, immediate and delayed posttests. The study also analysed the language-related episodes (LREs) occurring in the collaborative dialogue during the treatment sessions to identify the factors affecting uptake and retention of the corrective feedback in subsequent writing tasks. Findings revealed that both treatment groups outperformed the control group in the posttests, but, there was no significant difference between the unfocused and focused corrective feedback groups. Evidence from the LREs analysis suggests that extensive engagement in all the three functions of the Swain (2005) output hypothesis: noticing, hypothesis testing and metalinguistic, during the collaborative dialogue contribute toward the enhancement of uptake and retention. Since both correction types were equally facilitative in increasing accuracy of preposition usage, teachers may consider using them accordingly in writing tasks