Effect of different stimuli on twitching behavior of endophytic bacteria isolated from Loranthus sp. Jacq

Motility behavior and physiological response mechanisms of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress: Insights from individual cells to populations

The motility behaviors at the individual-cell level and the collective physiological responsive behaviors of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress were investigated. The results revealed that as salinity increased, electron transport activity and adenosine triphosphate content decreased from 15.75 μg O2/g/min and 593.51 mM/L to 3.27 μg O2/g/min and 5.34 mM/L, respectively, at 40 g/L, leading to a reduction in the rotation velocity and vibration amplitude of strain HNR. High salinity stress (40 g/L) down-regulated genes involved in ABC transporters (amino acids, sugars, metal ions, and inorganic ions) and activated the biofilm-related motility regulation mechanism in strain HNR, resulting in a further decrease in flagellar motility capacity and an increase in extracellular polymeric substances secretion (4.08 mg/g cell of PS and 40.03 mg/g cell of PN at 40 g/L). These responses facilitated biofilm formation and proved effective in countering elevated salt stress in strain HNR. Moreover, the genetic diversity associated with biofilm-related motility regulation in strain HNR enhanced the adaptability and stability of the strain HNR populations to salinity stress. This study enables a deeper understanding of the response mechanism of aerobic denitrifiers to high salt stress.

Seasonal Variation Imparts the Shift in Endophytic Bacterial Community Between Mango and its Hemiparasites

The study of community composition and community structure is important to know the ecological behaviour and community dynamics of the participating species and to understand the molecular interplay that lies between them. The community diversity greatly lies in the physiological status of the host and the environmental factors. The present study aims to explore the endophytic bacterial communities and their dynamics in the pre-flowering and post-flowering seasons in the horticulturally important Mango (Mangifera indica L.) and its hemiparasites: Loranthus parasiticus (L.) Marr. and Macrosolen colchinchinensis (Lour.) Tiegh. through a metagenomic approach using the sequence of V3 region of 16S rRNA gene. The genera Bacillus, Acinetobacter and Corynebacterium, under the phyla Firmicutes, Proteobacteria and Actinobacteria, respectively, were found to be the most abundant genera present in mango and its hemiparasites. It was found that during the post-flowering season, the twigs and leaves of mango had lesser endophytes than in other seasons while the alpha-diversity indices of the representative genera were the highest in L. parasiticus during the same seasons. However, in M. colchinchinensis, the alpha diversity was also higher in the post-flowering season similar to another hemiparasite plant L. parasiticus. The ecological, taxonomic and complex correlation studies unravelled that the hemiparasites act as the potent reservoirs of endophytic communities throughout the year and during favourable conditions, these bacterial communities disseminate to the mango plant.