Itamar Soares de Melo

Selection of microorganisms degrading S-Metolachlor herbicide

The aim of this work was to study herbicide degradation through selected microorganisms from humus and soil subjected to different plantation systems. The following bacterial species were identified: Klebsiella pneumoniae pneumoniae GC s.B strain 1, Pseudomonas alcaligenes, Enterobacter aerogenes GC s.A and Klebsiella pneumoniae pneumoniae GC s.B strain 2. Growth studies yet suggested the possibility of a very long lag phase. Although, culture with the herbicide presented biofilm formation and there were color changes in the herbicide that could have interfered with the espectrophotometry readings. After 5 days of incubation at 35oC, the difference in the concentration of herbicide was 14.42% on average and after 10 days, 35.01%.

Changes in hyphal morphology due to chitosan treatment in some fungal species

In this work, changes in the hyphal morphology due to chitosan treatment in some fungal species were studied. Scanning electron microscope (SEM) observations revealed that chitosans with molar fraction of acetyl groups (FA 0.16 and 0.18) and degree of polymerization (DP 1,089 and 1,242) had a direct effect on the morphology of the chitosan-treated fungi, reflecting its potential for causing a delay in the growth of Alternaria alternata (500 µg × mL-1), Botrytis cinerea (1,000 µg × mL-1), Penicillium expansum (1,000 µg × mL-1) and Rhizopus stolonifer (500 µg × mL-1). Mycelial aggregation and structural changes such as excessive branching, swelling of the cell wall and hyphae size reduction were observed in the micrographs.

Antibacterial Compounds from Marine Bacteria, 2010–2015

This review summarizes the reports on antibacterial compounds that have been obtained from marine-derived bacteria during the period 2010-2015. Over 50 active compounds were isolated during this period, most of which (69%) were obtained from Actinobacteria. Several compounds were already known, such as etamycin A (11) and nosiheptide (65), and new experiments with them showed some previously undetected antibacterial activities, highlighting the fact that known natural products may be an important source of new antibacterial leads. New broad-spectrum antibacterial compounds were reported with activity against antibiotic resistant Gram-positive and Gram-negative bacteria. Anthracimycin (33), kocurin (66), gageotetrins A-C (72-74), and gageomacrolactins 1-3 (86-88) are examples of compounds that display promising properties and could be leads to new antibiotics. A number of microbes produced mixtures of metabolites sharing similar chemical scaffolds, and structure-activity relationships are discussed.

Streptomyces araujoniae Produces a Multiantibiotic Complex with Ionophoric Properties to Control Botrytis cinerea

A recently described actinomycete species (Streptomyces araujoniae ASBV-1(T)) is effective against many phytopathogenic fungi. In this study, we evaluated the capacity of this species to inhibit Botrytis cinerea development in strawberry pseudofruit, and we identified the chemical structures of its bioactive compounds. An ethyl acetate crude extract (0.1 mg ml(-1)) of ASBV-1(T) fermentation broth completely inhibited fungus growth in strawberry pseudofruit under storage conditions. The crude extract was fractionated by preparative high-performance liquid chromatography; the active fraction was further evaluated by tandem mass spectrometry. ASBV-1(T) produced a multiantibiotic complex with ionophoric properties. This complex contained members of the macrotetralides class (including monactin, dinactin, trinactin, and tetranactin) and the cyclodepsipeptide valinomycin, all of which were active against B. cinerea. Furthermore, the addition of 2 mM MgSO4 and 1 mM ZnSO4 enhanced macrotetralide and valinomycin production, respectively, in the culture broth. These compounds are considered to be the main active molecules that S. araujoniae produces to control B. cinerea. Their low to moderate toxicity to humans and the environment justifies the application of ASBV-1(T) in biological control programs that aim to mitigate the damage caused by this phytopathogen.

Antifungal Activity of Pseudomonas frederiksbergensis CMAA 1323 Isolated from the Antarctic Hair Grass Deschampsia antarctica

Aims: Epiphytic bacteria, isolated from Deschampsia antarctica, were screened for their potential to inhibit the plant pathogen Botrytis cinerea, the causal agent of gray mold disease of strawberry pseudofruits. This phytopathogenic fungus is more active and the disease is more serious in temperate climate where the temperatures are lower. Methodology: The approach involved the isolation and characterization of bacteria from the phyllosphere of D. antarctica and the evaluation of their antifungal activity. Results: A total of 56 bacterial strains were isolated and only one of them, identified by the sequencing of 16S rDNA gene, as Pseudomonas frederiksbergensis CMAA 1323, inhibited the mycelial growth and the conidial germination of the fungus. Its ethyl acetate extract also inhibited Original Research Article Melo et al.; BMRJ, 14(3): 1-11, 2016; Article no.BMRJ.25314 2 the mycelial growth. Analysis of the bioactive fraction by using liquid chromatography coupled to a mass spectrometry (LC-MS) revealed the presence of cyclo(Pro-Val), a compound belonging to the class of diketopiperazines (DKPs). Conclusion: These findings support the potential use of the psychrophilic bacterium P. frederiksbergensis as promising antifungal agent, and highlight the need for more studies with this bacterium in the biological control of plant pathogenic fungi.

Bioprospecção em linhagens de Trichoderma spp. da floresta amazônica que inibem Pythium aphanidermatum por compostos orgânicos voláteis

Resumo O controle biológico vem sendo muito utilizado na agricultura moderna e os fungos do gênero Trichoderma são conhecidos por possuirem potencial no controle biológico. Portanto, o trabalho objetivou selecionar linhagens com potencial de inibição contra o fungo fitopatógeno Pythium aphanidermatum por meio da produção de compostos orgânicos voláteis, o qual permitiu selecionar 102 linhagens com potenciais de controle para o fitopatógeno.

A rapid primary screening method for antitumor using the oomycete Pythium aphanidermatum.

Investigating bioactive components from microbial metabolites can provide potential source for drug discovery. There are a number of traditional antitumor compounds screening assays already described. In this study, we have developed an efficient method to search for antitumor compounds using the Oomycete Pythium aphanidermatum as model on agar plates for high throughtput screening. Antioomycete compounds showed cytotoxic effects in human cancer cells lines due to the possible similarity between the lipid cell membrane of the Pythium species and cancerous cells, suggesting the compounds act through similar mechanisms of inhibition. In this assay, it is possible to evaluate hundreds of samples, with results in few hours. The Pythium assay was shown to be sensitive for several chemical substances and allowed the detection and isolation of antitumor compounds from microorganisms. This bioassay was shown to be sensitive, rapid, simple and reliable for antitumor activity. It takes just few hours to evaluate the properties of the extracts.

UV-B resistant yeast inhabit the phyllosphere of strawberry.

The increase on the worldwide influx of solar ultraviolet radiation (UV-B) has inflicted a considerable challenge, due to its deleterious effects to live beings and pose a special threat to phyllosphere communities. However, UV-B influence on epiphytic yeasts associated with agricultural crops remains limited. Main aim of the present study was to determine the effect of ultraviolet-B radiation on the epiphytic yeast populations associated with strawberry under field conditions. Thus, strawberries (Fragaria x ananassa Duchesne cv. Oso Grande) were grown under three different treatments: a) environmental UV-B, b) enhanced UV-B and c) decreased UV-B; thereafter, their yeast epiphytic populations were analyzed by T-RFLP prior to yeast isolation, identification and in vitro test for the sensitivity against UV-B. Our results demonstrated that UV-B radiation did not significantly affect the strawberry epiphytic yeast populations. However, isolates directly exposed to radiation, generally revealed morphological abnormalities and a diminishing Short Research Article British Microbiology Research Journal, 4(10): 1105-1117, 2014 1106 value in the percentage of survival, although they remained constant after 240 min of exposure. The increase in UV-B radiation was not sufficient to affect the dynamics and composition of epiphytic yeast communities from strawberry, there was a clear morphotype shift towards the selection of pigmented isolates.