Regulation of an endophytic nitrogen-fixing bacteria GXS16 promoting drought tolerance in sugarcane

Biodegradation of 1,2,4-trimethylbenzene in seawater using Rhodomonas sp. JZB-2: Performance, kinetics, and mechanism

Recently, marine ecosystems have been threatened by an accidental spill of C9 aromatics, particularly 1,2,4-trimethylbenzene (1,2,4-TMB), due to its high proportion in C9 aromatics. Microalgae-mediated bioremediation is a promising approach for pollutant removal owing to its eco-friendliness and carbon sequestration potential. In this study, the marine Cryptophyta Rhodomonas sp. JZB-2 demonstrated the ability to completely degrade 1-40 mg/L of 1,2,4-TMB within 6 days, showcasing its advantage in degrading 1,2,4-TMB at high concentrations compared to other microorganisms in the literature. Transcriptomics and proteomics analysis showed that several enzymes involved in 1,2,4-TMB degradation were significantly upregulated: hydroxylase (JmjC domain), iron/manganese-superoxide dismutase, and alcohol dehydrogenase etc. A new insight of biodegradation mechanism was elucidated that 1,2,4-TMB was initially oxidized by hydroxylase (JmjC domain) to 2,3,6-trimethylphenol, a process accelerated by the overexpression of iron/manganese-superoxide dismutase. Subsequently, 2,3,6-trimethylphenol was further degraded into 5-methylhexanoic acid via alcohol dehydrogenase and other short-chain dehydrogenases. Notably, the degradation products were less toxic than the parent compound (1,2,4-TMB). This study highlights the potential of Rhodomonas sp. JZB-2 for bioremediation of seawater contaminated with 1,2,4-TMB.

Exploring physiological and molecular dynamics of drought stress responses in plants: challenges and future directions

Plants face multifactorial environmental stressors mainly due to global warming and climate change which affect their growth, metabolism, and productivity. Among them, is drought stress which alters intracellular water relations, photosynthesis, ion homeostasis and elevates reactive oxygen species which eventually reduce their growth and yields. In addition, drought alters soil physicochemical properties and beneficial microbiota which are critical for plant survival. Recent reports have shown that climate change is increasing the occurrence and intensity of drought in many regions of the world, which has become a primary concern in crop productivity, ecophysiology and food security. To develop ideas and strategies for protecting plants against the harmful effects of drought stress and meeting the future food demand under climatic calamities an in-depth understanding of molecular regulatory pathways governing plant stress responses is imperative. In parallel, more research is needed to understand how drought changes the features of soil, particularly microbiomes, as microorganisms can withstand drought stress faster than plants, which could assist them to recover. In this review we first discuss the effect of drought stress on plants, soil physicochemical properties and microbiomes. How drought stress affects plant microbe interactions and other microbe-driven beneficial traits was also highlighted. Next, we focused on how plants sense drought and undergo biochemical reprogramming from root to shoot to regulate diverse adaptive traits. For instance, the role of calcium (Ca2+), reactive oxygen species (ROS) and abscisic acid (ABA) in modulating different cellular responses like stomata functioning, osmotic adjustment, and other adaptive traits. We also provide an update on the role of different hormones in drought signaling and their crosstalk which allows plants to fine tune their responses during drought stress. Further, we discussed how recurrent drought exposure leads to the development of short-term memory in plants that allows them to survive future drought stresses. Lastly, we discussed the application of omics and biotechnological-based mitigating approaches to combat drought stress in sustainable agriculture. This review offers a deeper understanding of multiple factors that are related to drought stress in plants which can be useful for drought improvement programs.

Enhancing sugarcane's drought resilience: the influence of Streptomycetales and Rhizobiales

Drought stress is a critical environmental factor affecting sugarcane yield, and the adaptability of the sugarcane rhizosphere bacterial community is essential for drought tolerance. This review examines the adaptive responses of sugarcane rhizosphere bacterial communities to water stress and explores their significant role in enhancing sugarcane drought tolerance. Under drought conditions, the sugarcane rhizosphere bacterial community undergoes structural and functional shifts, particularly the enrichment of beneficial bacteria, including Streptomycetales and Rhizobiales. These bacteria enhance sugarcane resilience to drought through various means, including nutrient acquisition and phytohormone synthesis. Furthermore, changes in the rhizosphere bacterial community were closely associated with the composition and levels of soil metabolites, which significantly influenced the physiological and biochemical processes of sugarcane during drought stress. This study deepens our understanding of rhizosphere bacterial communities and their interactions with sugarcane, laying a scientific foundation for developing drought-resistant sugarcane varieties, optimizing agricultural practices, and opening new avenues for agricultural applications.

Adsorption, natural attenuation, and microbial community response of ofloxacin and oxolinic acid in marine sediments

The pollution of quinolone antibiotics in the marine environment has attracted widespread attention, especially for ofloxacin (OFL) and oxolinic acid (OXO) due to their frequent detection. However, few studies have been conducted to assess the behaviors and microbial community response to these antibiotics in marine sediments, particularly for potential antibiotic-resistant bacteria. In this work, the adsorption characteristics, natural attenuation characteristics, and variation of microbial communities of OFL and OXO in marine sediments were investigated. The adsorption process of antibiotics in sediments occurred on the surface and internal pores of organic matter, where OFL was more likely to be transferred from seawater to sediment compared with OXO. Besides, the adsorption of two antibiotics on sediment surfaces was attributed to physisorption (pore filling, electrostatic interaction) and chemisorption (hydrogen bonding). The natural attenuation of OFL and OXO in marine sediment followed second-order reaction kinetics with half-lives of 6.02 and 26.71 days, respectively, wherein biodegradation contributed the most to attenuation, followed by photolysis. Microbial community structure in marine sediments exposure to antibiotics varied by reducing abundance and diversity of microbial communities, as a whole displaying as an increase in the relative abundance of Firmicutes whereas a decrease of Proteobacteria. In detail, Escherichia-Shigella sp., Blautia sp., Bifidobacterium sp., and Bacillus sp. were those antibiotic-resistant bacteria with potential ability to degrade OFL, while Bacillus sp. may be resistant to OXO. Furthermore, functional predictions indicated that the microbial communities in sediment may resist the stress caused by OFL and OXO through cyano-amino acid metabolism, and ascorbate and aldarate metabolism, respectively. The research is key to understanding fate and bacterial resistance of antibiotics in marine sediments.