Physiological and Transcriptome Response of the Polycyclic Aromatic Hydrocarbon Degrading Novosphingobium sp. LH128...

Area of Science:

• Environmental microbiology
• Bioremediation

Background:

• Soil bioaugmentation aims to enhance pollutant degradation using introduced microorganisms.
• A significant decrease in Colony Forming Units (CFU) is often observed post-inoculation, but the underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate the physiological and transcriptomic responses of Novosphingobium sp. LH128 upon inoculation into phenanthrene-spiked soil.
• To elucidate the reasons behind the rapid CFU reduction observed in bioaugmentation contexts.

Main Methods:

• Utilized a GFP-tagged variant of Novosphingobium sp. LH128 for monitoring.
• Assessed CFU counts and microscopic cell density at various time points post-inoculation.
• Performed transcriptome analysis to examine gene expression patterns.

Main Results:

• A 99% reduction in CFU was observed within 4 hours, while microscopic counts remained high, indicating a shift to a Viable But Non-Culturable (VBNC)-like state.
• Transcriptome analysis revealed upregulated phenanthrene degradation and stress response genes, suggesting active metabolism under stress.
• CFU numbers recovered to initial levels between 4 hours and 10 days.

Conclusions:

• Novosphingobium sp. LH128 enters a VBNC-like state in soil but remains metabolically active.
• The VBNC state is a critical factor to consider when evaluating the efficacy of bioaugmentation strategies.