Study of phenanthrene utilizing bacterial consortia associated with cowpea (Vigna unguiculata) root nodules

Prevalence, diversity and applications potential of nodules endophytic bacteria: a systematic review

Legumes are renowned for their distinctive biological characteristic of forming symbiotic associations with soil bacteria, mostly belonging to the Rhizobiaceae familiy, leading to the establishment of symbiotic root nodules. Within these nodules, rhizobia play a pivotal role in converting atmospheric nitrogen into a plant-assimilable form. However, it has been discerned that root nodules of legumes are not exclusively inhabited by rhizobia; non-rhizobial endophytic bacteria also reside within them, yet their functions remain incompletely elucidated. This comprehensive review synthesizes available data, revealing that Bacillus and Pseudomonas are the most prevalent genera of nodule endophytic bacteria, succeeded by Paenibacillus, Enterobacter, Pantoea, Agrobacterium, and Microbacterium. To date, the bibliographic data available show that Glycine max followed by Vigna radiata, Phaseolus vulgaris and Lens culinaris are the main hosts for nodule endophytic bacteria. Clustering analysis consistently supports the prevalence of Bacillus and Pseudomonas as the most abundant nodule endophytic bacteria, alongside Paenibacillus, Agrobacterium, and Enterobacter. Although non-rhizobial populations within nodules do not induce nodule formation, their presence is associated with various plant growth-promoting properties (PGPs). These properties are known to mediate important mechanisms such as phytostimulation, biofertilization, biocontrol, and stress tolerance, emphasizing the multifaceted roles of nodule endophytes. Importantly, interactions between non-rhizobia and rhizobia within nodules may exert influence on their leguminous host plants. This is particularly shown by co-inoculation of legumes with both types of bacteria, in which synergistic effects on plant growth, yield, and nodulation are often measured. Moreover these effects are pronounced under both stress and non-stress conditions, surpassing the impact of single inoculations with rhizobia alone.

Assessment of Phenanthrene Degradation Potential by Plant-Growth-Promoting Endophytic Strain Pseudomonas chlororaphis 23aP Isolated from Chamaecytisus albus (Hacq.) Rothm

Polycyclic aromatic hydrocarbons (PAHs) are common xenobiotics that are detrimental to the environment and human health. Bacterial endophytes, having the capacity to degrade PAHs, and plant growth promotion (PGP) may facilitate their biodegradation. In this study, phenanthrene (PHE) utilization of a newly isolated PGP endophytic strain of Pseudomonas chlororaphis 23aP and factors affecting the process were evaluated. The data obtained showed that strain 23aP utilized PHE in a wide range of concentrations (6-100 ppm). Ethyl-acetate-extractable metabolites obtained from the PHE-enriched cultures were analyzed by gas chromatography-mass spectrometry (GC-MS) and thin-layer chromatography (HPTLC). The analysis identified phthalic acid, 3-(1-naphthyl)allyl alcohol, 2-hydroxybenzalpyruvic acid, α-naphthol, and 2-phenylbenzaldehyde, and allowed us to propose that the PHE degradation pathway of strain 23aP is initiated at the 1,2-, 3,4-carbon positions, while the 9,10-C pathway starts with non-enzymatic oxidation and is continued by the downstream phthalic pathway. Moreover, the production of the biosurfactants, mono- (Rha-C8-C8, Rha-C10-C8:1, Rha-C12:2-C10, and Rha-C12:1-C12:1) and dirhamnolipids (Rha-Rha-C8-C10), was confirmed using direct injection-electrospray ionization-mass spectrometry (DI-ESI-MS) technique. Changes in the bacterial surface cell properties in the presence of PHE of increased hydrophobicity were assessed with the microbial adhesion to hydrocarbons (MATH) assay. Altogether, this suggests the strain 23aP might be used in bioaugmentation-a biological method supporting the removal of pollutants from contaminated environments.

Endophytic Bacteria in in planta Organopollutant Detoxification in Crops

Microbe-assisted organopollutant removal, or in planta crop decontamination, is based on an interactive system between organopollutant-degrading endophytic bacteria (DEB_OP) and crops in alleviating organic toxins in plants. This script focuses on the fast-growing body of literature that has recently bloomed in organopollutant control in agricultural plants. The various facets of DEB_OP under study include their colonization, distribution, plant growth-promoting mechanisms, and modes of action in the detoxification process in plants. Also, an assessment of the biotechnological advances, advantages, and bottlenecks in accelerating the implementation of this decontamination strategy will be undertaken. The highlighted key research directions from this review will shape the future of agro-environmental sustainability and preservation of human health.