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.
Ginger (Zingiber officinale Roscoe) is an economically and medicinally important spice crop, but its cultivation is severely affected by soft rot disease. In the present study, Fusarium solani (F. solani) associated with ginger soft rot was isolated, identified, and used as the target pathogen for antifungal evaluation. Diseased ginger rhizomes were collected from Gangapur village, Bahraich, Uttar Pradesh, India. The pathogen was isolated on potato dextrose agar (PDA), characterized morphologically and microscopically, and confirmed as F. solani through ITS sequencing and phylogenetic analysis. The antifungal potential of Trachyspermum ammi (T. ammi) essential oil was then evaluated against F. solani under in vitro conditions and supported by in silico analysis. The essential oil showed strong activity with a minimum inhibitory concentration (MIC) of 0.20 µL/mL and a minimum cidal concentration (MCC) of 0.60 µL/mL. The minimum killing time (MKT) of pure oil was 40 s, while the oil at its MCC required 24 h. Antifungal toxicity persisted at high inoculum density and remained stable after heating to 80°C and autoclaving. Molecular docking of F. solani cutinase indicated strongest binding for thymol, followed by p-cymene and γ-terpinene. These findings highlight the potential of T. ammi essential oil as an eco-friendly antifungal agent for managing F. solani-associated ginger soft rot.
