ABSTRACT The present study focuses on the bioprospection of plant growth‐promoting rhizobacteria (PGPR), with particular emphasis on ACC deaminase (ACCD) production. In a preliminary screening, rhizospheric soil from seven weed plants from the semidesert of Coahuila was collected, and 55 ACCD+ bacteria were isolated in DF (Dworkin and Foster) medium supplemented with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) as the unique source of nitrogen. The isolates exhibited multiple plant growth‐promoting (PGP) traits, including nitrogen fixation, high phosphate solubilization index, and high indole‐3‐acetic acid levels. Additionally, α‐ketobutyrate quantification was used to assess ACC deaminase activity across all isolates; M4B4, M2B4, and M1B7 exhibited high activity, at 0.94, 3.27, and 3.62 µmol KB mg −1 h −1 , respectively. Consequently, these three isolates were evaluated for saline and drought stress assays under in vitro conditions, with M2B4 showing slight growth at 1% NaCl; meanwhile, M2B4 and M4B4 showed greater increases with 5% polyethylene glycol. Bioassays on Arabidopsis thaliana Col‐0 inoculated with M4B4 significantly increased foliar area under in vitro conditions. The growth‐promoting effect was evaluated in wheat ( Triticum aestivum L.); M4B4 significantly increased root dry biomass compared with control plants. In wheat plants under abiotic stress, M2B4 exhibited greater size and stem diameter than the control at 175 mM NaCl, and M4B4 showed increased stem diameter at 200 mM. Furthermore, drought‐stressed wheat plants with M4B4 showed reduced stomatal conductance and transpiration. The isolates M2B4 and M4B4 were categorized as ACCD+ rhizobacteria and identified as Serratia and Citrobacter , respectively. Overall, these isolates have high potential as bioinoculants.
ABSTRACT Nitrous oxide (N 2 O) released from wastewater treatment plants (WWTPs) is largely governed by the metabolism of dominant resident microorganisms, yet how interactions among co‐occurring denitrifiers shape the net fate of N 2 O remains poorly resolved. Here, a defined two‐member consortium was assembled, comprising Acinetobacter johnsonii (AJ), a frequently recovered species in wastewater treatment plants, and Comamonas testosteroni (CT); its denitrification behaviour was dissected using time‐resolved performance assays, a nitrogen mass balance, 16S rRNA community tracking, and quantitative proteomics. All cultures removed more than 99% of influent NO 3 − –N (initial ~100 mg N/L) within 12 h. In monoculture, CT accumulated more N 2 O (4.11 µg L −1 N 2 O–N) and less residual nitrite, whereas AJ showed the opposite pattern (0.28 µg L −1 N 2 O–N). The 1:1 consortium reconciled both liabilities, limiting nitrite build‐up and holding N 2 O–N to 0.37 µg L −1 , approximately one order of magnitude below CT. CT expressed a canonical periplasmic denitrification module (periplasmic nitrate reductase NapAB and norB, a cbb3‐type cytochrome‐c oxidase related to nitric oxide reductase) but lacked detectable nitrous oxide reductase (NosZ), consistent with partial denitrification and N 2 O accumulation. AJ instead expressed an assimilatory nitrate‐reduction repertoire (nitrate transporter F946_02194 and NAD(P)H‐dependent nitrite reductase subunits F946_02190/02191), consistent with nitrate assimilation into biomass rather than complete denitrification to N 2 . We propose thcD‐derived electron cross‐feeding from CT to AJ supports this assimilatory route, consistent with redirecting nitrogen away from gaseous intermediates. The consortium raised intracellular nitrogen to 25.3% of the initial nitrogen pool while minimising N 2 O, suggesting a community‐engineering principle for low‐N 2 O nitrogen removal.
ABSTRACT Agricultural soils contain mixture of metals, pesticides, antibiotics, pharmaceuticals, and plastics. Their combined effects are shaped by contaminant chemistry, root activity, and microbial interactions at the rhizosphere interface. This review develops a mechanistic framework linking co‐contaminant exposure with root sensing, exudate reprogramming, microbiome reassembly, multitrophic interactions, microbial detoxification, and plant stress adaptation. We distinguish taxonomic shifts from functional resilience and microbial resistance from plant protection. Particular attention is given to cross‐kingdom interactions and microbial processes that control contaminant sequestration, transformation, nutrient availability, and host signaling. Multi‐omics approaches are evaluated alongside stable‐isotope probing, synthetic communities, metabolite supplementation, and genetic validation to identify candidate mechanisms for targeted causal validation. We then discuss microbiome engineering strategies for moving beyond descriptive community profiling toward predictive and function‐oriented rhizosphere engineering. These strategies can be guided by contaminant fate and plant performance. By integrating contaminant chemistry, root–microbiome signaling, microbial functional responses, and plant adaptation, this review provides a mechanistic framework for understanding and engineering rhizosphere resilience under co‐contaminant stress.
ABSTRACT Live cell imaging is a useful tool for studying community interactions, morphological development, and population variance in microbial research. Here, we aim to develop a new approach to monitor the time until germination and the hyphal development rate of filamentous fungi at an individual level. Conidia of 19 Aspergillus species, including some xerophilic, were suspended in liquid Sabouraud medium, and conidia were tracked for 96 h using real‐time imaging. A sorting algorithm was developed to categorize conidia into germinated or non‐germinated pools based on a decrease in circularity and an increase in area. The increase in area used in the sorting algorithm was species‐specific and was derived using segmented linear regression to determine the inflection point of area increase, which served as a proxy for the transition from isotropic to polarized growth. Of the 19 species measured, 15 germinated within 96 h. In the germinated species, we measured the hyphal growth rate until the experiment termination or until conidia exited the imaging frame. Hyphal growth rates were calculated both on the individual conidium level and using growth models on data from the first 24 h post germination. This methodology enabled a high‐throughput, species‐specific, and individual approach when comparing germination metrics. The live‐cell imaging approach for monitoring fungal germination and hyphal growth rate provides an important framework for studying fungal development and has the potential to offer in‐depth insights into early fungal growth that may be overlooked by conventional endpoint assays.
Arbuscular mycorrhizal fungi (AMF) are widespread root-associated fungi that contribute to plant nutrient acquisition and soil ecosystem processes. However, information on the distribution of Glomoid and non-Glomoid AMF associated with Solanaceae hosts in the northwestern Himalaya remains limited. The present study evaluated the diversity, distribution, and observed host occurrence patterns of AMF associated with tomato (Solanum lycopersicum), capsicum (Capsicum annuum), eggplant (Solanum melongena), and black nightshade (Solanum nigrum). A total of 72 AMF morphotaxa representing 13 genera were recovered from the rhizosphere soils, of which 39 taxa (54.2%) belonged to the Glomoid taxonomic group and 33 taxa (45.8%) to the non-Glomoid taxonomic group. Glomoid taxa showed higher occurrence frequency and broader observed host distribution, with Glomus constrictum and Septoglomus deserticola recorded in all four hosts. Non-Glomoid AMF contributed 45.8% of total richness and included a higher proportion of taxa observed in a single host. AMF richness varied among host species, with capsicum and eggplant supporting greater observed richness than tomato and black nightshade. Diversity indices were generally higher for Glomoid taxa, whereas evenness did not differ significantly between the two taxonomic groups. Overall, the study provides baseline information on AMF richness and distribution associated with cultivated and wild Solanaceae in the northwestern Himalaya. The observed occurrence patterns represent associations within the sampled hosts and should not be interpreted as evidence of confirmed host specialization or functional differentiation. Molecular identification, quantitative community data, environmental variables, and multivariate analyses will be required to investigate the ecological factors underlying these distribution patterns.
