Winning and losing with microbes: how microbially mediated fitness differences influence plant diversity

Interactions between plants and soil microbes can strongly influence plant diversity and community dynamics. Soil microbes may promote plant diversity by driving negative frequency‐dependent plant population dynamics, or may favor species exclusion by providing one species an average fitness advantage over others. However, past empirical research has focused overwhelmingly on the consequences of frequency‐dependent feedbacks for plant species coexistence and has generally neglected the consequences of microbially mediated average fitness differences. Here we use theory to develop metrics that quantify microbially mediated plant fitness differences, and show that accounting for these effects can profoundly change our understanding of how microbes influence plant diversity. We show that soil microbes can generate fitness differences that favour plant species exclusion when they disproportionately harm (or favour) one plant species over another, but these fitness differences may also favor coexistence if they trade off with competition for other resources or generate intransitive dominance hierarchies among plants. We also show how the metrics we present can quantify microbially mediated fitness differences in empirical studies, and explore how microbial control over coexistence varies along productivity gradients. In all, our analysis provides a more complete theoretical foundation for understanding how plant–microbe interactions influence plant diversity.     

Virulence and pathogenicity of a Candida albicans mutant with reduced filamentation

Deletion of DNA polymerase eta (Rad30/Polη) in pathogenic yeast Candida albicans is known to reduce filamentation induced by serum, ultraviolet, and cisplatin. Because nonfilamentous C. albicans is widely accepted as avirulent form, here we explored the virulence and pathogenicity of a rad30Δ strain of C. albicans in cell‐based and animal systems. Flow cytometry of cocultured fungal and differentiated macrophage cells revealed that comparatively higher percentage of macrophages was associated with the wild‐type than rad30Δ cells. In contrast, higher number of Polη‐deficient C. albicans adhered per macrophage membrane. Imaging flow cytometry showed that the wild‐type C. albicans developed hyphae after phagocytosis that caused necrotic death of macrophages to evade their clearance. Conversely, phagosomes kill the fungal cells as estimated by increased metacaspase activity in wild‐type C. albicans. Despite the morphological differences, both wild‐type and rad30? C. albicans were virulent with a varying degree of pathogenicity in mice models. Notably, mice with Th1 immunity were comparatively less susceptible to systemic fungal infection than Th2 type. Thus, our study clearly suggests that the modes of interaction of morphologically different C. albicans strains with the host immune cells are diverged, and host genetic background and several other attributing factors of the fungus could additionally determine their virulence.     

Autophagy–virus interplay in plants: from antiviral recognition to proviral manipulation

Autophagy is a conserved self-cleaning and renewal system required for cellular homeostasis and stress tolerance. Autophagic processes are also implicated in the response to ‘non-self’ such as viral pathogens, yet the functions and mechanisms of autophagy during plant virus infection have only recently started to be revealed. Compelling evidence now indicates that autophagy is an integral part of antiviral immunity in plants. It can promote the hypersensitive cell death response upon incompatible viral infections or mediate the selective elimination of entire particles and individual proteins from compatible viruses in a pathway similar to xenophagy in animals. Several viruses, however, have evolved measures to antagonize xenophagic degradation or utilize autophagy to suppress disease-associated cell death and other defence pathways like RNA silencing. Here, we highlight the current advances and gaps in our understanding of the complex autophagy–virus interplay and its consequences for host immunity and viral pathogenesis in plants.     

Tiger cowrie Cypraea tigris feeds on coral-competing sponge Rhabdastrella globostellata in an Acropora dominated reef of Gulf of Mannar,India

Gulf of Mannar (GoM) in the southeast coast of India is known for its coral reefs and reef-associated biodiversity. Corals in GoM were affected to a significant extent by climate change-driven coral bleaching in 2016, and are currently recovering. After the bleaching mortality that corals suffered, the competition for space between corals and sponges is obvious in GoM. Rhabdastrella globostellata is a common marine sponge found overgrowing live coral colonies of the patch reefs in GoM at Pattinamaruthoor in March 2019. Underwater assessment of the reef revealed that 60.06% live coral cover was dominated by Acropora corals (81.91%). Among the acroporans 8.23% of colonies were found overgrown by R. globostellata. During the night dives the tiger cowrie Cypraea tigris was observed to feed on R. globostellata. From this observation the present study infers that C. tigris helps the corals fight these sponges, and concludes that tiger cowries should be protected and promoted to tackle climate change implications.     

Bovicins: The Bacteriocins of Streptococci and Their Potential in Methane Mitigation

Probiotics and Antimicrobial Proteins - Bovicin is a type AII lantibiotic, possessing two β-methyllanthionine and a disulfide bridge encoded by bovA gene hitherto unknown a couple of decades...     

Effect of Lactobacillus rhamnosus NCDC 298 with FOS in Combination on Viability and Toxin Production of Enterotoxigenic Escherichia coli

Probiotics and Antimicrobial Proteins - The present study was to investigate the utilization of prebiotics by Lactobacillus rhamnosus NCDC 298 and its synergistic adversary effect on both...     

Probiotics L. acidophilus and B. clausii Modulate Gut Microbiota in Th1- and Th2-Biased Mice to Ameliorate Salmonella Typhimurium-Induced Diarrhea

Gut microbiota play important role in maintaining health. Probiotics are believed to augment it further. We aimed at comparing effects of probiotics, Lactobacillus acidophilus (LA) and Bacillus clausii (BC) (a) on the gut microbiota abundance and diversity and (b) their contributions to control intestinal dysbiosis and inflammation in Th1- and Th2-biased mice following Salmonella infection. We report how could gut microbiota and the differential immune bias (Th1 or Th2) of the host regulate host responses when challenged with Salmonella typhimurium in the presence and absence of either of the probiotics. LA was found to be effective in ameliorating the microbial dysbiosis and inflammation caused by Salmonella infection, in Th1 (C57BL/6) and Th2 (BALB/c)-biased mouse. BC was able to ameliorate Salmonella-induced dysbiosis and inflammation in Th2 but not in Th1-biased mouse. These results may support probiotics LA as a treatment option in the case of Salmonella infection.

     

Integration of diffraction phase microscopy and Raman imaging for label‐free morpho‐molecular assessment of live cells

Label‐free quantitative imaging is highly desirable for studying live cells by extracting pathophysiological information without perturbing cell functions. Here, we demonstrate a novel label‐free multimodal optical imaging system with the capability of providing comprehensive morphological and molecular attributes of live cells. Our morpho‐molecular microscopy (3M) system draws on the combined strength of quantitative phase microscopy (QPM) and Raman microscopy to probe the morphological features and molecular fingerprinting characteristics of each cell under observation. While the commonr‐path geometry of our QPM system allows for highly sensitive phase measurement, the Raman microscopy is equipped with dual excitation wavelengths and utilizes the same detection and dispersion system, making it a distinctive multi‐wavelength system with a small footprint. We demonstrate the applicability of the 3M system by investigating nucleated and nonnucleated cells. This integrated label‐free platform has a promising potential in preclinical research, as well as in clinical diagnosis in the near future.