N-134. Phosphate and Phosphonate Use by Microorganisms Isolated from Hypersaline Environments of the Great Salt Lake, Utah
The Great Salt Lake (GSL) contains high levels of phosphate (PO43-), however most is precipitated with minerals such as calcium and magnesium and is not bioavailable for microorganisms. Organic compounds are probably a major source of PO43- in this environment. However, little is known about the microorganisms involved with the PO43- cycle in the GSL. Using a non-specific saline medium, organisms were isolated from water and sediment from the south arm (8% saline) and the north arm (22% saline) of the GSL. These isolates were characterized by colony morphology, Gram stain, and 16S rRNA gene sequence. Isolates that amplified with Bacteria specific primers from the north arm were related to the halophilc genera Salicola, Halomonas, or Marinobacter, while isolates from the south arm were related to Halomonas and Salinivibrio. Two isolates from the north arm amplified only with Archaea primers and were related to the genera Natronococcus and Haloarcula. The ability of the isolates to grow with organic phosphate esters (o-phosphorylethanolamine, o-phospho-DL-serine), organic phosphonates (1-aminoethylphosphonic acid, n-(phosphonomethyl)glycine), or inorganic PO43- (KH2PO4, H3PO4) as the sole PO43- source was determined. Each isolate was inoculated into a row of a 96 well plate containing a PO43--free minimal medium, and triplicate columns were amended with 1 mM of one of the PO43- sources listed above. Growth was monitored by measuring absorbance at 595 nm. Compared to the no-phosphate control, most isolates could use several of the PO43- sources, but individual isolates preferred some PO43- sources over others. All of the isolates could grow on media containing KH2PO4 as the sole PO43- source. However, several also grew quickly on 1-aminoethylphosphonic acid indicating the ability to cleave the C-P bond of the phosphonate molecule. Conversely, organisms grew slowly, or not at all, with n-(phosphonomethyl)glycine, the active component of the herbicide Roundup, suggesting toxicity. Some isolates grew slowly with no added PO43-, indicating these organisms may have efficient mechanisms for scavenging very low levels of available PO43-.