The Ecological Coherence of Temperature and Salinity Tolerance Interaction and Pigmentation in a Non-marine Vibrio Isolated from Salar de Atacama

Abstract

The occurrence of microorganisms from the Vibrio genus in saline lakes from northern Chile had been evidenced using Numerical Taxonomy decades before and, more recently, by phylogenetic analyses of environmental samples and isolates. Most of the knowledge about this genus came from marine isolates and showed temperature and salinity to be integral agents in shaping the niche of the Vibrio populations. The stress tolerance phenotypes of Vibrio sp. Teb5a1 isolated from Salar de Atacama was investigated. It was able to grow without NaCl and tolerated up to 100 g/L of the salt. Furthermore, it grew between 17° and 49°C (optimum 30°C) in the absence of NaCl, and the range was expanded into cold temperature (4-49°C) in the presence of the salt. Other additional adaptive strategies were observed in response to the osmotic stress: pigment production, identified as the known antibacterial prodigiosin, swimming and swarming motility and synthesis of a polar flagellum. It is possible to infer that environmental congruence might explain the cellular phenotypes observed in Vibrio sp. considering that coupling between temperature and salinity tolerance, the production of antibacterial agents at higher temperatures, flagellation and motility increase the chance of Vibrio sp. to survive in salty environments with high daily temperature swings and UV radiation.

Keywords: Vibrio; halotolerant; osmotic-stress; prodigiosin; psychrotolerant.

FIGURE 1

Adaptation growth curves of Vibrio sp. in presence of NaCl. Vibrio sp. cells were adapted previously to grow in presence of 0 g/L NaCl and KCl (), 25 g/L NaCl () and 100 g/L NaCl (). New cultures were prepared from these cells and used to perform their respective curves.

FIGURE 2

Growth curves of Vibrio sp. at different temperatures in presence and absence of NaCl. (A) Vibrio sp. cells grown in absence of salt (0 g/L NaCl) (B) Vibrio sp. cells grown in presence of salt (25 g/L NaCl). The temperature was changed from 4° to 49°C under both growth conditions.

FIGURE 3

Effect of salinity on the pigmentation of Vibrio sp. Cells were previously adapted to grow in presence of different salt concentration and temperatures, showing non-accumulation of pigment in absence of NaCl.

FIGURE 4

Swimming and swarming motilities of Vibrio sp. The microorganism was adapted to grow with 0 g/L NaCl (A,C) and 25 g/L NaCl (B,D). Cells were inoculated in their respective salts concentration in the swim (A,B) and swarm (C,D) plates and photographed after 72 h of incubation at 30°C. The arrows and white circles highlight the single colonies in absence of NaCl.

FIGURE 5

NaCl-dependent flagellum in Vibrio sp. Cells were grown in 0 g/L (A) and 25 g/L (B) NaCl and analyzed by transmission electron microscopy. Arrows indicate the presence of dense granules and flagella, respectively.