title: Isolation and in vitro selection of actinomycetes strains as potential probiotics for aquaculture.
abstract: OBJECTIVE
  This study was designed to describe a series of in vitro tests that may aid the discovery of probiotic strains from actinomycetes.
  
  
  METHODS
  Actinomycetes were isolated from marine sediments using four different isolation media, followed by antimicrobial activity and toxicity assessment by the agar diffusion method and the hemolysis of human blood cells, respectively. Extracellular enzymatic production was monitored by the hydrolysis of proteins, lipids and carbohydrates. Tolerance to different pH values and salt concentrations was also determined, followed by hydrophobicity analysis and genetic identification of the most promising strains.
  
  
  RESULTS
  Five out of 31 isolated strains showed antimicrobial activity against three Vibrio species. Three non-hemolytic strains (N7, RL8 and V4) among these active isolates yielded positive results in hydrophobicity tests and exhibited good growth at salt concentrations ranging from 0% to 10%, except strain RL8, which required a salt concentration >0.6%. Although these strains did not grow at pH<3, they showed different enzymatic activities. Phylogenetic analysis revealed that strains N7 and V4 have more than 99% identity with several Streptomyces species, whereas the closest matches to strain RL8 are Streptomyces panacagri and Streptomyces flocculus, with 98% and 98.2% similarity, respectively.
  
  
  CONCLUSIONS
  Three actinomycetes strains showing probiotic-like properties were discovered using several in vitro tests that can be easily implemented in different institutions around the world.
authors.affiliation: Department of Microbiology, Center for the Study of Bioactive Chemicals (CBQ), Central University "Marta Abreu" of Las Villas. Road to Camajuaní Km 5½. Santa Clara 54830. Villa Clara. Cuba.
authors.forename: Milagro García
authors.initials: MG
authors.lastname: Bernal
authors.affiliation: Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita Sur, C.P. 23090. La Paz, Baja California Sur, México.
authors.forename: Ángel Isidro
authors.initials: ÁI
authors.lastname: Campa-Córdova
authors.affiliation: Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita Sur, C.P. 23090. La Paz, Baja California Sur, México.
authors.forename: Pedro Enrique
authors.initials: PE
authors.lastname: Saucedo
authors.affiliation: Department of Microbiology, Center for the Study of Bioactive Chemicals (CBQ), Central University "Marta Abreu" of Las Villas. Road to Camajuaní Km 5½. Santa Clara 54830. Villa Clara. Cuba.
authors.forename: Marlen Casanova
authors.initials: MC
authors.lastname: González
authors.affiliation: Department of Microbiology, Center for the Study of Bioactive Chemicals (CBQ), Central University "Marta Abreu" of Las Villas. Road to Camajuaní Km 5½. Santa Clara 54830. Villa Clara. Cuba.
authors.forename: Ricardo Medina
authors.initials: RM
authors.lastname: Marrero
authors.affiliation: Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita Sur, C.P. 23090. La Paz, Baja California Sur, México.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Mazón-Suástegui
keywords: Vibrio; aquaculture; marine actinomycetes; probiotics