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Division of single host cells after infection with chlamydiae
Abstract:
Mouse fibroblasts (L cells) were infected in suspension with Chlamydia psittaci (6BC) and then plated out on a solid substrate at a density of 80 cells per cm2 so that the effect of chlamydial infection on the division of single host cells and their progeny could be determined. Uninfected L cells multiplied with a mean generation time of 15 h. The generation time of single L cells infected with 1.5 50% infectious units (ID50) of C. psittaci was over twice as long. Half of the infected L cells had divided once by day 4 after infection, and the rest had divided more than once. Division of infected cells frequently produced one infected and one uninfected daughter. About half of the L cells infected with 15 ID50 of C. psittaci divided at least once before most of them detached from their substrate before observation on day 3. Less than 10% of the L cells infected with 75 ID50 of C. psittaci divided before they were lost from their substrate by day 2. Comparable results were obtained with single L cells infected with a lymphogranuloma venereum (440L) strain of C. trachomatis and with single HeLa 229 cells infected with C. psittaci. It was concluded that high multiplicities of infection of host cells with chlamydiae quickly bring cell division to a halt, whereas lower multiplicities slow but do not immediately stop the division of host cells. However, indefinitely multiplying clones of chlamydia-infected host cells were not observed. The method used here should be applicable to other studies on the division of cells in culture.
Insights
Chlamydial infections significantly slow host cell division, with high doses halting it entirely. While some infected cells divide, producing mixed progeny, indefinitely multiplying infected cell clones were not observed.
Area of Science:
- Cell Biology
- Microbiology
- Infectious Diseases
Background:
- Chlamydial infections impact host cell functions.
- Understanding the effect of Chlamydia on host cell division is crucial.
Purpose of the Study:
- To investigate how Chlamydia psittaci infection affects the division of single mouse fibroblast (L cells).
- To determine the impact of varying infection multiplicities on host cell proliferation.
Main Methods:
- Infecting L cells with Chlamydia psittaci (6BC strain) at different multiplicities (1.5, 15, 75 infectious doses 50%).
- Plating infected cells on a solid substrate to monitor division of single cells and their progeny.
- Comparing division rates and generation times of infected versus uninfected L cells.
Main Results:
- Chlamydial infection significantly increased the mean generation time of L cells, more than doubling it at low multiplicities.
- High infection doses (75 ID50) rapidly halted cell division, with most cells detaching by day 2.
- Lower doses (1.5 ID50) slowed division, and infected cells sometimes produced one infected and one uninfected daughter cell.
- No indefinitely multiplying clones of chlamydia-infected host cells were observed.
Conclusions:
- High multiplicities of Chlamydia infection quickly inhibit host cell division.
- Lower multiplicities slow but do not immediately stop host cell division.
- The study presents a viable method for studying host cell division dynamics during infection.