Some properties of an unidentified halophile: growth characteristics, internal salt concentration, and morphology

An unidentified halophile isolated from plates of a complex agar medium containing 4.25 M NaCl showed optimum growth in broths containing 0.5-1.0 M NaCl but exhibited a wide range of growth from 0.045-4.5 M. The organism can be classified as a facultative halophile with wide salt tolerance. Logarithmic phase cells grown in media containing 0.5 M NaCl were rod-shaped in long chains which changed to smaller, single, or paired cells in stationary growth. The internal Na+ and K+ concentrations were 0.05 M and 0.34 M for logarithmic phase cells and 0.29 and 0.32 M for stationary phase cells. In 4.3 M NaCl media the cells were rod-shaped throughout the growth cycle, occurring primarily in pairs. The internal Na+ K" concentrations in cells in logarithmic phase growth were 0.62 M and 0.58 M while in stationary phase growth these values were 1.01 M and 0.66 M respectively. In contrast, logarithmic phase cells of the extreme halophile Halobacterium cutirubrum had internal Na+ and K+ concentrations of 0.80 M and 5.32 M when grown in 3.3 M NaCl. The internal Na+ and K+ concentrations, therefore, in the unidentified halophile do not resemble those found in H. cutirubrum but are much closer to those present in Escherichia coli.