The increasing need for sustainable agricultural practices, combined with the demand for enhanced crop productivity, has led to a growing interest in utilizing microorganisms for biocontrol of diseases and pests, as well as for growth promotion. In Brazilian agriculture, the use of plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting fungi (PGPF) has become increasingly prevalent, with a corresponding rise in the number of registered microbial inoculants each year. PGPR and PGPF occupy diverse niches within the rhizosphere, playing a crucial role in soil nutrient cycling and influencing a wide range of plant physiological processes. This review examines the primary mechanisms employed by these microbial agents to promote growth, as well as the strategy of co-inoculation to enhance product efficacy. Furthermore, we provide a comprehensive analysis of the microbial inoculants currently available in Brazil, detailing the microorganisms accessible for major crops, and discuss the market’s prospects for the research and development of novel products in light of current challenges faced in the coming years.

Low phosphorus (P) availability in tropical soils is one of the main constraints to agricultural productivity and the sustainability of cropping systems. In this study, we evaluated the functional potential of four bacterial strains, including those present in two commercial inoculants: Nodubiophos (Ag87-CCT 8090 and Ag94-CCT 8108), and Biomaphos (B119 and B2084), focusing on their production of phosphatase and phytase enzymes, organic acids, and their agronomic efficacy in soybean cultivation. In vitro assays showed that all strains exhibited phytase and both acid and alkaline phosphatase activities, with B2084 and Ag94 standing out in phytase-mediated mineralization. In contrast, B119 and B2084 showed the highest phosphatase activity. Organic acid production varied among strains and was influenced by the phosphate source, indicating a highly responsive metabolic regulation. Strains Ag87 and Ag94 were particularly effective in producing lactic, malic, and gluconic acids, displaying distinct profiles modulated by the available P source. In field trials, combined inoculation with Ag87 and Ag94 led to increased soybean yield, achieving performance comparable to conventional fertilization at 50% and 100% of the recommended P rate, despite applying only 30% of the total P. The results highlight complementary metabolic strategies among the evaluated strains, with the ability to solubilize and mineralize phosphorus through different mechanisms. They support their potential use as bioinoculants to enhance nutrient use efficiency and reduce fertilizer dependency in soybean cultivation.

Fluopsin C (FlpC) is an organocupric secondary metabolite with low-molecular-weight, produced by some Pseudomonas and Streptomyces bacteria. The compound was identified in 1970 as prismatic dark-green crystals, with strong antimicrobial activity against several human and phytopathogens. Due to its high cytotoxicity, research on this compound decreased after the 1970s. During the early 2000s, FlpC gained more attention as a promising compound by which to develop new antimicrobials to control human, animal, and plant pathogens. This study provides an overview of the results pertaining to the in vitro and in vivo antimicrobial activity of pure FlpC, as well as semi-purified fractions containing FlpC, against phytopathogenic microorganisms. Furthermore, the bioprospection history of the extensively researched FlpC-producing Pseudomonas aeruginosa LV strain and the related molecular evidence regarding the compound’s biosynthesis are discussed. Overall, FlpC is proposed to be an important alternative to antimicrobial resistance in human and animal health, and in tackling the negative environmental impacts caused by the exacerbated use of pesticides against phytopathogens.

The antibiotic activity of metalloantibiotic compounds has been evaluated since the 90s, and many different modes of action were characterized. In the last decade, the effects of secondary metabolites produced by Pseudomonas aeruginosa LV strain, including a cupric compound identified as Fluopsin C, were tested against many pathogenic bacteria strains, proving their high antibiotic activity. In the present study, the bactericidal mechanisms of action of Fluopsin C and the semi-purified fraction F4A were elucidated. The results found in electron microscopy [scanning electron microscopy (SEM) and transmission electronic microscopy (TEM)] demonstrated that both Fluopsin C and F4A are affecting the cytoplasmatic membrane of Gram-positive and Gram-negative bacteria. These results were confirmed by fluorescence microscopy, where these bacteria presented permeabilization of their cytoplasmatic membranes after contact with the semi-purified fraction and pure compound. Using electronic and fluorescence microscopy, along with bacterial mutant strains with marked divisional septum, the membrane was defined as the primary target of Fluopsin C in the tested bacteria.

The demand for a more sustainable agriculture, coupled with the need for optimized crop productivity, has driven the use of microorganisms for the biocontrol of diseases and pests, as well as for growth promotion. The use of plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting fungi (PGPF) in Brazilian production systems has become increasingly common, with the number of microbial inoculant registrations in the country growing every year. PGPR and PGPF occupy various niches in the rhizosphere, playing a crucial role in soil nutrient cycling, as well as influencing various plant physiological processes. In this review, we address the main mechanisms used by these microbial agents in growth promotion and the use of strain co-inoculation as a strategy to enhance the efficacy of these products. Subsequently, we conduct an analysis of the available inoculants in Brazil, detailing the microorganisms available for the main Brazilian crops, and the prospects of this market regarding research and development of new products for the coming years based on the current challenges faced.

Acinetobacter baumannii emerged as one of the most important pathogens for the development of new antimicrobials due to the worldwide detection of isolates resistant to all commercial antibiotics, especially in nosocomial infections. Biofilm formation enhances A. baumannii survival by impairing antimicrobial action, being an important target for new antimicrobials. Fluopsin C (FlpC) is an organocupric secondary metabolite with broad-spectrum antimicrobial activity. This study aimed to evaluate the antibiofilm activity of FlpC in established biofilms of extensively drug-resistant A. baumannii (XDRAb) and the effects of its combination with polymyxin B (PolB) on planktonic cells. XDRAb susceptibility profiles were determined by Vitek 2 Compact, disk diffusion, and broth microdilution. FlpC and PolB interaction was assessed using the microdilution checkerboard method and time–kill kinetics. Biofilms of XDRAb characterization and removal by FlpC exposure were assessed by biomass staining with crystal violet. Confocal Laser Scanning Microscopy was used to determine the temporal removal of the biofilms using DAPI, and cell viability using live/dead staining. The minimum inhibitory concentration (MIC) of FlpC on XDRAb was 3.5 µg mL⁻¹. Combining FlpC + PolB culminated in an additive effect, increasing bacterial susceptibility to both antibiotics. FlpC-treated 24 h biofilms reached a major biomass removal of 92.40 ± 3.38% (isolate 230) using 7.0 µg mL⁻¹ FlpC. Biomass removal occurred significantly over time through the dispersion of the extracellular matrix and decreasing cell number and viability. This is the first report of FlpC’s activity on XDRAb and the compound showed a promissory response on planktonic and sessile cells, making it a candidate for the development of a new antimicrobial product.