IQUIBICEN   23947
INSTITUTO DE QUIMICA BIOLOGICA DE LA FACULTAD DE CIENCIAS EXACTAS Y NATURALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Effect on different pH on Pseudomonas extremaustralis growth and polyhydroxyalkanoates accumulation.
Autor/es:
LOPEZ, NANCY I.; DANIELA VERA; MARIA GABRIELA BRITO; LAURA J. RAIGER IUSTMAN
Lugar:
San Luis
Reunión:
Congreso; XIII Congreso Argentino de Microbiologia General SAMIGE 2018; 2018
Institución organizadora:
SAMIGE
Resumen:
P. extremaustralis is a versatile Antarctic bacterium able to grow under aerobic and microaerobic conditions and is related to several non-pathogenic Pseudomonads. An interesting characteristic of P. extremaustralis is its capability to accumulate polyhydroxyalkanoates (PHAs) as polyhydroxybutyrate (PHB) and medium chain length PHAs under unbalanced nutritional conditions. PHAs accumulation was shown to be related with P. extremaustralis high resistance to environmental stresses, having also biotechnological interest by its properties similar to petroleum derived plastics. Due that changes in the medium pH could be considered as a stress factor the aim of this work was to analyze the effect of different pH in P. extremaustralis growth and how pH affects PHAs accumulation.To study the effect of pH in P. extremaustralis growth, overnight precultures performed in LB medium supplemented with 0.25% sodium octanoate to favor PHA accumulation were used to inoculate fresh culture medium in which pH was adjusted to different values (5.5, 6, 7, 8, 9, 9.5 and 10). Initial OD600nm was 0.05 (about 1x107 CFU/ml). Cultures were incubated at 30ºC and 200 rpm for 24h. After incubation time, growth was measured by both OD and CFU/ml counts. Qualitative PHA accumulation was analyzed by Nile blue staining and microscopy observation. Quantitative PHA content was determined by gas chromatography. Experiments were performed using 3 independent cultures.Our results showed strong differences in the growth of the cells at different pH. Marked loss of viability at pH 5.5 was observed. The initial bacterial number decreased immediately 3 orders of magnitude (from about 107CFU/ml to 103 CFU/ml) and no viable cells were detected after 24h incubation. On the other hand, P. extremaustralis was able to grow when pH ranging between 6 to 9, showing a high increase in viable cell number and PHA content. For cultures grown at alkaline pH between 9 to 10, a decrease in viability of around two orders of magnitude in comparison with initial counts was observed and an increasing cell size associated to a greater PHAs synthesis was observed. Results showed that both acidic and alkaline pH affected growth of P. extremaustralis, however alkaline suboptimal growth conditions resulted in higher PHA accumulation.These results suggest that PHA conferred to P. extremaustralis an adaptive advantage, enabling it to survive under suboptimal conditions for growth. In addition information regarding conditions leading to higher PHA accumulation can be useful to improve the design of strategies for bio-plastics production.