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Gluconacetobacter diazotrophicus is an endophyte of sugarcane frequently found in plants grown in agricultural areas where nitrogen fertilizer input is low. Recent results from this laboratory, using mutant strains of G. diazotrophicus unable to fix nitrogen, suggested that there are two beneficial effects of G. diazotrophicus on sugarcane growth: one dependent and one not dependent on nitrogen fixation. A plant growth-promoting substance, such as indole-3-acetic acid (IAA), known to be produced by G. diazotrophicus, could be a nitrogen fixation-independent factor. One strain, MAd10, isolated by screening a library of Tn5 mutants, released only ~6% of the amount of IAA excreted by the parent strain in liquid culture. The mutation causing the IAA-phenotype was not linked to Tn5. A pLAFR3 cosmid clone that complemented the IAA deficiency was isolated. Sequence analysis of a complementing subcione indicated the presence of genes involved in cytochrome c biogenesis (ccm, for cytochrome c maturation). The G. diazotrophicus ccm operon was sequenced; the individual ccm gene products were 37 to 52% identical to ccm gene products of Escherichia coli and equivalent cyc genes of Bradyrhizobium japonicum. Although several ccm mutant phenotypes have been described in the literature, there are no reports of ccm gene products being involved in IAA production. Spectral analysis, heme-associated peroxidase activities, and respiratory activities of the cell membranes revealed that the ccm genes of G. diazotrophicus are involved in cytochrome c biogenesis.

Research was conducted to confirm nitrogen fixation under aerobic conditions in Acetobacter diazotrophicus PAL5. Results show active cells exhibit fully developed respiratory system and also fix nitrogen in contrast to the latter generally occurring under anerobic conditions.

Introduction: Recurrent urinary tract infections (RUTIs) caused by uropathogenic Escherichia coli are costly public health problems impacting patients' quality of life., Aim: In this work, a comparative genomics analysis of three clinical RUTI strains isolated from bladder biopsy specimens was performed., Materials and Methods: One hundred seventy-two whole genomes of urinary tract E. coli strains were selected from the NCBI database. The search for virulence factors, fitness genes, regions of interest, and genetic elements associated with resistance was manually carried out. The phenotypic characterization of antibiotic resistance, haemolysis, motility, and biofilm formation was performed. Moreover, adherence and invasion assays with human bladder HTB-5 cells, and transmission electron microscopy (TEM) were performed., Results: The UTI-1&#95;774U and UTI-3&#95;455U/ST1193 strains were associated with the extraintestinal pathotypes, and the UTI-2&#95;245U/ST295 strain was associated with the intestinal pathotype, according to a phylogenetic analysis of 172 E. coli urinary strains. The three RUTI strains were of clinical, epidemiological, and zoonotic relevance. Several resistance genes were found within the plasmids of these strains, and a multidrug resistance phenotype was revealed. Other virulence genes associated with CFT073 were not identified in the three RUTI strains (genes for type 1 and P fimbriae, haemolysin hlyA, and sat toxin). Quantitative adherence analysis showed that UTI-1&#95;774U was significantly ( p  < 0.0001) more adherent to human bladder HTB-5 cells. Quantitative invasion analysis showed that UTI-2&#95;245U was significantly more invasive than the control strains. No haemolysis or biofilm activity was detected in the three RUTI strains. The TEM micrographs showed the presence of short and thin fimbriae only in the UTI-2&#95;245U strain., Conclusion: The high variability and genetic diversity of the RUTI strains indicate that are a mosaic of virulence, resistance, and fitness genes that could promote recurrence in susceptible patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Flores-Oropeza, Ochoa, Cruz-Córdova, Chavez-Tepecano, Martínez-Peñafiel, Rembao-Bojórquez, Zavala-Vega, Hernández-Castro, Flores-Encarnacion, Arellano-Galindo, Vélez-Sánchez and Xicohtencatl-Cortes.)

The purification and characterization of AAT1, one of two aromatic amino acid aminotransferase (EC 2.6.1.57) in Azospirillum brasilense, is described. Purified AAT1 had a subunit mass of 33 kDa and a nondenatured molecular mass of 66 kDa, suggesting a dimeric structure. Other properties include a pI of 5.04, an optimum temperature of 45 degrees C, and optimum pH of 8.5. AAT1 utilized all aromatic amino acids, the L-tryptophan derivatives such as L-5-methyl tryptophan and L-flour-tryptophan, and L-histidine. The apparent Km values for L-tyrosine, L-phenylalanine, and L-tryptophan were 0.19, 0.43, and 1.05 mM, respectively. The enzyme was competive inhibited by indole-3-pyruvic acid with a Ki of 0.17 mM.