Carotenoids are highly important in pigmentation, and its content in farmed crustaceans and fish correlates to their market value. These pigments also have a nutritional role in aquaculture where they are routinely added as a marine animal food supplement to ensure fish development and health. However, there is little information about carotenoids obtained from Antarctic bacteria and its use for pigmentation improvement and flesh quality in aquaculture. This study identified carotenoids produced by Antarctic soil bacteria. The pigmented strain (CN7) was isolated on modified Luria–Bertani (LB) media and incubated at 4 °C. This Gram-negative bacillus was identified by 16S rRNA analysis as Flavobacterium segetis. Pigment extract characterization was performed through high-performance liquid chromatography (HPLC) and identification with liquid chromatography–mass spectrometry (LC–MS). HPLC analyses revealed that this bacterium produces several pigments in the carotenoid absorption range (six peaks). LC–MS confirms the presence of one main peak corresponding to lutein or zeaxanthin (an isomer of lutein) and several other carotenoid pigments and intermediaries in a lower quantity. Therefore, we propose CN7 strain as an alternative model to produce beneficial carotenoid pigments with potential nutritional applications in aquaculture.

In this study, bacterial isolates C1-4-7, D2-4-6, and M1-4-11 from Antarctic soil were phenotypically and genotypically characterized, and their antibacterial spectrum and that of cell-free culture supernatant were investigated. Finally, the effect of temperature and culture medium on the production of antimicrobial compounds was investigated. The three bacteria were identified as different strains of the genus Pseudomonas. The three bacteria were multi-drug resistant to antibiotics. They exhibited different patterns of growth inhibition of pathogenic bacteria. M1-4-11 was remarkable for inhibiting the entire set of pathogenic bacteria tested. All three bacteria demonstrated optimal production of antimicrobial compounds at 15 °C and 18 °C. Among the culture media studied, Nutrient broth would be the most suitable to promote the production of antimicrobial compounds. The thermostability exhibited by the antimicrobial molecules secreted, their size of less than 10 kDa, and their protein nature would indicate that these molecules are bacteriocin-like compounds.

En este estudio 50 aislados bacterianos obtenidos de muestras de suelo antártico prístino, de las islas Rey George y Greenwich (Islas Shetland del Sur), y 25 aislados bacterianos de la rizósfera de Deschampsia antarctica Desv, se emplearon para determinar su capacidad antimicrobiana y su respuesta a 21 antibióticos. La susceptibilidad a los antibióticos se evaluó siguiendo el método de difusión en disco utilizando diferentes grupos de antibióticos: penicilinas, cefalosporinas, carbapenémicos, aminoglicósidos, quinolonas, tetraciclina, fenicoles, macrólidos, sulfonamidas y trimetoprim. La producción de compuestos antimicrobianos por los aislados bacterianos antárticos se determinó mediante el método de difusión en agar, utilizando como indicadores un panel de bacterias patógenas humanas Gram positivo y Gram negativo. Los aislados bacterianos estudiados mostraron resistencia a 14 (67%) de los 21 antibióticos probados. Tres aislados bacterianos (4%) fueron resistentes a al menos un antibiótico y 47 (63%) fueron multirresistentes. Además, 26 aislados bacterianos (35%) no muestran actividad antimicrobiana y fueron susceptibles a todos los antibióticos estudiados. Finalmente, 27 aislados bacterianos (36%) combinaron actividad antimicrobiana y resistencia múltiple a antibióticos y en promedio presentaron resistencia a 10 antibióticos. Los aislados bacterianos que combinan actividad antimicrobiana y resistencia múltiple a los antibióticos son especialmente interesantes ya que es probable que estas dos capacidades proporcionen una ventaja competitiva a las bacterias antárticas para permitirles sobrevivir en un entorno hostil. Adicionalmente, estos aislados bacterianos son nuevas fuentes potenciales de compuestos activos para el control de microorganismos patógenos.

La disminución sostenida de la disponibilidad de nuevas moléculas antimicrobianas para el uso terapéutico en las últimas décadas y el gran aumento de microorganismos resistentes a estos compuestos hace necesario buscar nuevas sustancias con propiedades antimicrobianas. Los ambientes extremos, donde hay poca disponibilidad de nutrientes, son escenarios propicios para buscar este tipo de compuestos, ya que las bacterias compiten entre sí y con otros organismos por posicionarse en el nicho ecológico y secretan, asociado a su metabolismo secundario, una serie de moléculas que inhiben o matan a otros microorganismos, evitando su multiplicación. Nuestro grupo posee una colección de bacterias aisladas de la rizósfera de suelo del continente antártico, que logran crecer en condiciones de deprivación alimenticia y a 4 ºC. Debido al hábitat extremo donde se desarrollan, las bacterias de los suelos de la Antártica están en una constante competencia por lo recursos nutricionales, desarrollando distintas estrategias para colonizar su nicho ecológico y competir con otros microorganismos de la microbiota Antártica. En base a lo anterior, el objetivo de este trabajo consistió en identificar bacterias aisladas de la rizosfera de Deschampsia antarctica Desv capaces de inhibir no solo el crecimiento de microorganismos de su entorno, sino que también de bacterias y hongos patógenos para humanos. A partir de una colección de 55 aislados de la rizósfera de la planta D. antarctica Desv. se identificó 11 aislados con capacidad de matar o inhibir bacterias patógenas humanas pero ningún aislado inhibió el crecimiento del hongo Candida albicans. Los resultados mostraron que las 11 bacterias antárticas con actividad antibacteriana corresponden a bacilos aerobios estrictos, Gram negativo, con características de pertenecer al género Pseudomonas.

Low fermentation temperatures are usually employed to obtain high-quality wines. This is especially interesting for white wine production since it prevents the loss of volatile compounds and a browning appearance; however, available fermentative yeasts do not usually tolerate low temperatures. Therefore, an interesting place to find new yeasts with cryotolerance is the Antarctic continent. From soil samples collected in Antarctica, 125 yeasts were isolated, of which 25 exhibited fermentative activity at 10 °C. After a fingerprinting assay, we classified the candidates into nine isotypes and sequenced internal transcribed spacer regions for their identification. These yeasts were identified as part of the Mrakia genus. Sugar and alcohol tolerance tests showed that some of these Antarctic soil yeasts were able to grow up to 9% alcohol, and 25% sugar was reached; however, they exhibited longer latency periods compared to the control Saccharomyces cerevisiae. The optimal growing temperature for the isolated Antarctic yeasts was between 10 °C and 15 °C. A comprehensive analysis of the results obtained showed that the isolates 10M3-1, 4M3-6, and 4B1-35 could be good candidates for fermentation purposes due to their alcohol, sugar tolerance, and growth features. Our results prove that it is possible to isolate fermentative yeasts from Antarctic soil with promising characteristics for their potential use in the wine production industry.