Liquid Fungal Cocultivation as a Strategy to Access Bioactive Metabolites.

Fungi are a rich source of bioactive compounds. Fungal cocultivation is a method of potentiating chemical interactions and, consequently, increasing bioactive molecule production. In this study, we evaluated the bactericidal, antiprotozoal, and cathepsin V inhibition activities of extracts from axenic cultures of 6 fungi (Fusarium guttiforme, Pestalotiopsis diospyri, Phoma caricae-papayae, Colletotrichum horii, Phytophthora palmivora, and C. gloeosporioides) that infest tropical fruits and 57 extracts obtained by their cocultivation. Our results reveal that fungal cocultivation enhances the biological activity of the samples, since all extracts that were active on Gram-positive bacteria, Gram-negative bacteria, Trypanosoma cruzi, and Leishmania infantum were obtained from cocultivation. Bacterial growth is either totally or partially inhibited by 46% of the extracts. Two extracts containing mainly fusaric and 9,10-dehydrofusaric acids were particularly active. The presence of the fungus F. guttiforme in co-cultures that give rise to extracts with the highest activities against L. infantum. An axenic culture gave rise to the most active extract for the inhibition of cathepsin V; however, other coculture extracts also exhibited activity toward this biological target. Therefore, the results of the biological activities indicate that fungal cocultivation increased the biological potential of samples, likely due to the hostile and competitive environment that pushes microorganisms to produce substances important for defense and allows access to metabolic routes then silenced in milder cultivation conditions.

Synthesis and Antibacterial Activity of Polyalthic Acid Analogs.

Polyalthic acid (PA) is a diterpene found in copaiba oil. As a continuation of our work with PA, we synthesized PA analogs and investigated their antibacterial effects on preformed biofilms of Staphylococcus epidermidis and determined the minimal inhibitory concentration (MIC) of the best analogs against planktonic bacterial cells. There was no difference in activity between the amides 2a and 2b and their corresponding amines 3a and 3b regarding their ability to eradicate biofilm. PA analogs 2a and 3a were able to significantly eradicate the preformed biofilm of S. epidermidis and were active against all the Gram-positive bacteria tested (Enterococcus faecalis, Enterococcus faecium, S. epidermidis, Staphylococcus aureus), with different MIC depending on the microorganism. Therefore, PA analogs 2a and 3a are of interest for further in vitro and in vivo testing to develop formulations for antibiotic drugs against Gram-positive bacteria.

Endophytic and rhizospheric bacteria associated with Paspalum atratum and its potential for plant growth promotion with different phosphate sources.

The genus Paspalum belongs to the family Poaceae and has several species that are native to Brazil. The Paspalum Germplasm Bank (GB) of the Brazilian Agricultural Research Corporation comprises approximately 450 accessions from 50 species. Among these accessions, Paspalum atratum (BGP 308) has economic potential for forage purposes. However, the endophytic and rhizospheric microbial communities within this accession and their ability to promote plant growth remain unknown. The present study aimed to isolate the endophytic and rhizospheric bacteria associated with P. atratum and to assess their potential for plant growth improvement, so-called plant growth-promoting bacteria (PGPB). For the in vitro tests, the ability of nitrogen-fixing bacteria (NFB), phosphate solubilization (PS) and indoleacetic acid (IAA) production were evaluated. A total of 116 endophytic and rhizosphere bacteria were obtained from the isolation. In the in vitro tests, 43 (37.00%) of these isolates showed positive NFB, PS, and IAA results. These isolates were identified by 16S rDNA sequencing. The phosphate solubilization index (PSI) ranged from 2 to 3.61, all 43 strains performed biological nitrogen fixation and the IAA production ranged from 12.85 to 431.41 µg ml-1. Eight of these 43 isolates were evaluated in vivo in a greenhouse using P. atratum caryopsis. The pots were filled with soil prepared with three different phosphate sources and one control without phosphate. After growth, the plants were submitted to morphological, bromatological and chemical determination. Data were analyzed using analysis of variance (ANOVA) and principal component analysis (PCA). In the in vivo test, treatments 105 (Pseudomonas sp.) and 458 (Pseudomonas sp.) were the most significant for the crystalline phosphate source, 109 (Bacillus sp.) for the sedimentary phosphate source and, as for the soluble phosphate source most treatments that received bacterial isolates had higher phosphorus content in the dry matter than the uninoculated soluble phosphate control. The 105FCR (crystalline phosphate + Pseudomonas sp.), 109FSE (sedimentary phosphate + Bacillus sp.), and 110 FSE (sedimentary phosphate + Enterobacter sp.) treatments showed the best results for plant growth promotion. This work made it possible to determine the bacterial community associated with P. atratum (BGP308) and to obtain new potential plant growth-promoting strains.