Staphylococcus aureus Membrane Vesicles and Its Potential Role in Bacterial Pathogenesis

The production of extracellular vesicles is a ubiquitous process in both Gram-negative and Gram-positive bacteria. Gram-negative bacteria produce and secrete outer membrane vesicles during in vitro culture and in vivo infection and their contribution to bacterial pathogenesis has been well characterized. However, little is known about extracellular vesicles in Gram-positive bacteria. Until now, only few Gram-positive bacterial species, Staphylococcus aureus, Bacillus anthracis, B. cereus, and B. subtilis, have been found to produce membrane vesicles (MVs), but their contribution to bacterial pathogenesis has not been understood. Here, I discuss S. aureus MVs in terms of MV production, interaction of MVs with host cells, and immune response against MVs to understand its potential role in S. aureus pathogenesis.

Molecular battles between plant and pathogenic bacteria in the phyllosphere

The phyllosphere, i.e., the aerial parts of the plant, provides one of the most important niches for microbial colonization. This niche supports the survival and, often, proliferation of microbes such as fungi and bacteria with diverse lifestyles including epiphytes, saprophytes, and pathogens. Although most microbes may complete the life cycle on the leaf surface, pathogens must enter the leaf and multiply aggressively in the leaf interior. Natural surface openings, such as stomata, are important entry sites for bacteria. Stomata are known for their vital role in water transpiration and gas exchange between the plant and the environment that is essential for plant growth. Recent studies have shown that stomata can also play an active role in limiting bacterial invasion of both human and plant pathogenic bacteria as part of the plant innate immune system. As counter-defense, plant pathogens such as Pseudomonas syringae pv tomato (Pst) DC3000 use the virulence factor coronatine to suppress stomate-based defense. A novel and crucial early battleground in host-pathogen interaction in the phyllosphere has been discovered with broad implications in the study of bacterial pathogenesis, host immunity, and molecular ecology of bacterial diseases.