Diversity and metabolic abilities of antarctic bacteria - Polyhydroxyalkanoate production by Antarctic soil bacteria

Bacterial isolates were obtained from soil samples collected from various locations around Casey station. Soil samples were serial diluted in sterile water and plated on low-strength nutrient agar containing cycloheximide. The agar plates were incubated at 5 degrees C until colonies were observed. Bacterial colonies were picked and purified on fresh agar plates.

The bacterial isolates were screened for the production of polyhydroxyalkanoates (PHA) by growing them in nitrogen-limiting medium. PHA in the cells was detected by Nile Blue A staining and by Nile Red staining of the colonies. PHA-producing isolates were tested with individual carbon sources i.e. glucose, sodium octanoate and saponified palm kernel oil. The intracellular PHA was extracted by chloroform, precipitated by methanol, and analysed by gas-chromatography (GC) to determine the monomer compositions. Selected PHA-producing isolates were identified by their 16S rRNA gene sequences.

Two main groups of PHA-producing bacteria were identified from among the isolates: Janthinobacterium spp. which produce polyhydroxybutyrate (PHB) from glucose, and Pseudomonas spp. which produce medium-chain-length PHA (mcl-PHA) from octanoate. Some but not all of the Pseudomonas isolates were able to produce mcl-PHA from glucose. The monomer composition of the mcl-PHA produced by these Pseudomonas strains was found to be related to the carbon substrates fed to the bacteria.

In selected isolates, the PHA biosynthesis genes (phaC) and associated PHA depolymerase gene (phaZ) will be analysed and compared with those from non-antarctic bacteria.

The attached excel file lists the PHA-producing bacterial isolates obtained from various soil samples, and their closest homology to GenBank entry and type culture based on the 16S rRNA gene sequence.

Feb 2004 (soil samples collected by member from another research group) and
Dec 2005 (soil samples collected by C.W.Chong)

Soil samples were collected from the following locations:
- Around Casey station - (Red Shed, Lab building, etc)
- Peterson Island
- Around Wilkes Land (Wilkes Land, Whitney Point, Thala Valley)
- Browning Peninsula
- Mitchell Peninsula

Irene K. P. TAN - Project leader
Yuh Shan GOH - isolated and screened bacteria for polyhydroxyalkanoates (PHA); identified the PHA-producing bacterial isolates; characterised the PHA
Chun Wie CHONG - collected the soil samples from around Casey station in December 2005