Why does nitrogen depletion trigger PHA biosynthesis in Pseudomonas aeruginosa?

Nitrogen limitation halts cell division and redirects excess carbon from oil metabolism toward polyhydroxyalkanoate production as a carbon storage mechanism.

How does lipase secretion enable PHA production from edible oil?

Secreted lipases hydrolyze the oil substrate into fatty acids, which are then metabolized intracellularly into PHA precursors for polymerization.

What quantitative measurements indicate successful PHA accumulation in bacterial cells?

PHA accumulation is evidenced by increased cell size, formation of cytoplasmic inclusion bodies, and elevated biomass relative to growth phase.

Why is replication of nitrogen-limited conditions important for cross-functional collaboration?

Consistent replication ensures reliable PHA yield data, enabling alignment between microbiology, bioprocessing, and materials science teams on production scalability.

What statistical analysis is required to compare PHA yields under different carbon-to-nitrogen ratios?

Comparative analysis requires quantification of PHA per cell mass across replicates, using statistical tests to determine significant differences in polymer accumulation efficiency.

Biosynthesis of Polyhydroxyalkanoates by Pseudomonas aeruginosa in a Carbon-Rich Medium

JoVE Encyclopedia of Experiments

Microbiology

0 views • 1:29 min • October 30th, 2025

Begin with a strain of Pseudomonas aeruginosa bacteria, isolated from oil-contaminated soil, in a medium containing a nitrogen source and an excess of edible oil as the carbon source.

This strain synthesizes polyhydroxyalkanoate (PHA), a long-chain polymer useful in producing bioplastics.

Incubate under agitation to facilitate aeration and promote bacterial growth.

Initially, the medium supplies both carbon and nitrogen sources to support bacterial proliferation and generate high biomass.

After substantial growth, nitrogen depletion in the medium halts further cell division and redirects the excess carbon source toward PHA biosynthesis.

The bacteria secrete lipases that break down the oil into fatty acids, which are metabolized by intracellular enzymes into PHA precursors.

PHA synthase enzyme polymerizes these precursors into PHA.

PHA accumulates inside cytoplasmic granules, known as inclusion bodies, which leads to an increase in cell size.

The PHA-enriched bacterial biomass is now ready for downstream analyses.