FILAMENT FORMATION BY ESCHERICHIA COLI AT INCREASED HYDROSTATIC PRESSURES

Area of Science:

• Microbiology
• Cell Biology
• Biophysics

Background:

• Escherichia coli (E. coli) is a model organism for studying bacterial responses.
• Hydrostatic pressure is a significant environmental factor affecting microbial life.
• Understanding bacterial adaptation to pressure is crucial for various fields, including deep-sea microbiology and biotechnology.

Purpose of the Study:

• To investigate the effects of increased hydrostatic pressure on the growth, reproduction, and morphology of Escherichia coli.
• To determine the biochemical changes associated with filament formation in E. coli under high pressure.
• To explore the potential role of DNA replication in pressure-induced filamentation.

Main Methods:

• Culturing three different strains of E. coli at hydrostatic pressures ranging from 1 to 500 atm.
• Measuring bacterial growth via dry weight and protein content.
• Assessing bacterial reproduction through direct microscopic counts and plating on EMB Agar.
• Analyzing cell morphology, including filament length and biomass distribution.
• Quantifying cellular content of protein, RNA, and DNA per unit of biomass and per cell.

Main Results:

• Hydrostatic pressures from 200 to 500 atm significantly retarded both growth and reproduction of E. coli.
• E. coli cells formed long filaments at increased pressures, with lengths varying by strain (e.g., mean length of 5.82 μm for strain B at 475 atm vs. ~2 μm at 1 atm).
• Increased pressure led to higher RNA content and lower DNA content per unit of biomass, with RNA increasing with cell length while DNA remained constant, suggesting a failure in DNA replication.

Conclusions:

• Increased hydrostatic pressure inhibits E. coli cell division and promotes filament formation.
• The observed filamentation is likely due to a failure of DNA replication at elevated pressures, leading to a repression of cell division.
• These findings provide insights into the mechanisms of bacterial adaptation to extreme hydrostatic environments.