Biosynthesis of Cyclic Lipopeptides by Bacillus velezensis Bs006 and its Antagonistic Activity are Modulated by the Temperature and Culture Media Conditions.

Antagonistic activity of strains from Bacillus species has made them among the preferred agricultural biological control agents against phytopathogenic fungi. These microorganisms' success is mostly based on the production of antagonistic secondary metabolites, mainly those of the non-ribosomal cyclic lipopeptides (CLPs) nature, which can affect phytopathogens directly (iturins and fengycins) or indirectly (surfactins and fengycins). However, abiotic factors in the target site can influence the behavior of the biocontrol traits, but to date, few studies attempting to decipher this kind of interaction have been conducted. This work aimed to evaluate the effect of temperature and culture medium on growth, antagonistic activity against Fusarium oxysporum f. sp. physali (Foph), and the profile of CLPs produced by Bacillus velezensis Bs006. The data showed that measured traits in Bs006 varied with temperature and medium interaction. The concentration of CLPs, as well as the antagonistic activity against Foph, was increased as the nutritional wealth, temperature, and time of incubation increased. The concentration of fengycins and iturins was higher than surfactins at high temperatures. However, a bacteriostatic effect was detected with a combination of Landy medium and 15 °C, which prevented both the biosynthesis of CLPs and the antagonistic activity. The results of this work highlight the importance of abiotic conditions of the target site where a biocontrol agent will be applied to stay active and develop its full antagonistic potential. This response by Bs006 could partly explain the variability of its biocontrol efficacy in the Foph-golden berry pathosystem.

Filibacter tadaridae sp. nov., isolated from within a guano pile from a colony of Mexican free-tailed bats Tadarida brasiliensis.

A Gram-stain-positive, aerobic bacterium, TB-66T, was isolated from a pile of bat guano in a cave of New Mexico, USA. On the basis of 16S rRNA gene sequence similarity comparisons, strain TB-66Tgrouped together with Filibacter limicola showing a 16S rRNA gene sequence similarity of 98.5 % to the type strain. The quinone system of strain TB-66T consisted predominantly of menaquinone MK-7. The polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylserine and three unidentified phospholipids. The peptidoglycan type was A4α l-Lys-d-Glu (A11.33). The major fatty acids were C15 : 0 anteiso, C16 : 0, and C16 : 1 ω7c. The G+C content of the genomic DNA was 37.6 (±1.8) mol%. On the basis of the genotypic and phenotypic properties it is clear that strain TB-66T represents a member of the genus Filibacter, but is distinct from the only other species in the genus, Filibacter limicola DSM 13886T. We propose a novel species with the name Filibacter tadaridae sp. nov. The type strain is TB-66T (= CIP 111629T= LMG 30660T= CCM 8866T).

Evaluation of three methods for preservation of Azotobacter chroococcum and Azotobacter vinelandii

La preservación de bacterias es asunto de granimportancia debido a que muchas de ellas son usadas enprocesos biotecnológicos que requieren mantener su viabilidad ypropiedades genéticas. En este estudio, se evaluaron tres métodospara la preservación de A. chroococcum C26 y A. vinelandii C27;criopreservación, liofilización, e inmovilización en polímerossecos, durante 60, 30 y 60 días, respectivamente. A su vez, seestudió el efecto de tres agentes protectivos para la liofilizacióny para la criopreservación y cuatro polímeros. La eficiencia delos métodos fue evaluada contando células viables y midiendoactividad como fijación de nitrógeno. Los resultados mostraronque la mejor técnica, la cual mantuvo la viabilidad y la actividad,fue la liofilización, seguida por inmovilización y criopreservación.La liofilización mantuvo estable la habilidad bacteriana para fijarnitrógeno, la tasa de sobrevivencia bacteriana (TSB) fue superioral 80%; y el mejor resultado se evidenció cuando se usó S/BSAcomo agente protectivo. La inmovilización mantuvo la BSRsuperior al 80%, y la fijación de nitrógeno fue disminuida en 20%.La criopreservación tuvo pérdida sustancial de viabilidad para C26(TSB aprox. 70%); mientras que C27 se preservó bien. La fijaciónde nitrógeno fue significativamente disminuida para ambas cepasindependientemente del agente crioprotectivo usado (P < 0.05).Los resultados sugieren que el éxito de los métodos de preservaciónpara Azotobacter depende de la técnica, el agente protectivo y la cepausada; siendo la liofilización con S/BSA la técnica con mejoresresultados para preservar las bacterias de este género...

Because the use of bacteria for biotechnological processes requires maintaining their viability and geneticstability, preserving them becomes essential. Here, we evaluated three preservation methods for A.chroococcum C26 and A. vinelandii C27; preservation methods: cryopreservation and immobilization in drypolymers for 60 days, and freeze-drying for 30. We evaluated their efficiency by counting viable cells andmeasuring nitrogen fixation activity. Additionally, we assessed the effect of three protective agents forfreeze-drying, three for cryopreservation, and four polymers. Freeze-drying proved the best technique tomaintain viability and activity, followed by immobilization and cryopreservation. Bacterial nitrogen fixingability remained unchanged using the freeze-drying method, and bacterial survival exceeded 80%; S/BSAwas the best protective agent. Immobilization maintained bacterial survival over 80%, but nitrogen fixationwas decreased by 20%. Lastly, cryopreservation resulted in a dramatic loss of viability for C26 (BSRapprox. 70%), whereas C27 was well preserved. Nitrogen fixation for both strains decreased regardless ofthe cryoprotective agent used (P < 0.05). In conclusion, the success of Azotobacter preservation methodsdepend on the technique, the protective agent, and the strain used. Our results also indicated that freezedryingusing S/BSA is the best technique to preserve bacteria of this genus...

Porque o uso de bactérias para processos biotecnológicos,requer a manutenção da sua viabilidade e estabilidade genética,preserva-las é essencial Avaliaram-se três métodos de preservação deA. chroococcum C26 e A. vinelandii C27; criopreservação, liofilização, eimobilização de polímeros secos. Examinamos também o efeito deagentes protetores para liofilizar, para a criopreservação, e polímeros.A eficiência foi avaliada contando as células viáveis e medindoa atividade como a fixação do azoto. Os resultados mostraramque a melhor técnica foi a liofilização seguida de imobilização ecriopreservação. A liofilização manteve inalterada a capacidadeda bactéria para fixar o azoto, e o melhor resultado foi observadoquando se usou S/BSA como agente protetor. A criopreservaçãoresultou em uma perda dramática de viabilidade para C26 (TSBaprox. 70%.), enquanto que C27 foi bem preservada. A fixaçãode azoto foi significativamente diminuída para ambas as estirpes,independentemente do agente crioprotector utilizado (P < 0.05).Em conclusão, os resultados sugerem que o êxito dos métodosde conservação de Azotobacter dependem da técnica, do agente deproteção, e da estirpe utilizada, sendo a liofilizacao com S/BSA amelhor técnica para preservar as bactérias deste género...