Formation and Destruction of Internal Membranes in L Cells Infected with Chlamydia psittaci

Abstract

L cells (mouse fibroblasts), uninfected and infected with Chlamydia psittaci (meningopneumonitis strain), were labeled with "C-amino acids, and their membranous organelles were separated by isopycnic equilibrium centrifugation of whole cell homogenates on discontinuous sucrose density gradients. Incorporation of labeled amino acids into host and parasitic proteins was differentiated on the basis of susceptibility to cycloheximide. Twenty hours after infection with C. psittaci, incorporation of newly synthesized proteins into the internal membranes of L cells was almost completely inhibited, and internal membranes made prior to infection were altered or destroyed. The unit membrane that at all times surrounds the cytoplasmic vacuole containing the multiplying chlamydiae was made by the host from membranes or membrane precursors present before infection. No proteins synthesized by C. psittaci became associated with host cell membranes. Destruction or modification of the internal membranes of the host cell may be an integral part of the chlamydial developmental cycle.

Toxicity of Low and Moderate Multiplicities of Chlamydia psittaci for Mouse Fibroblasts (L Cells)

“…5B), lack of isoleucine only partially blocked the appearance of trypan bluepositive L cells. We cannot explain why feeding isoleucine 24 h after infection appears to have transiently protected L cells against chlamydial injury. Figure 5C differs from 5B only in that the 50-ID50 inoculum had been inactivated with ultraviolet light.…”

“…Table 4). Synthesis of DNA was severely inhibited by 24 h, synthesis of protein was strongly inhibited at 48 h but not at 24 h, and synthesis of RNA was hardly inhibited at all. Inhibition of macromolecule synthesis and the percentage of trypan blue-positive cells gave discordant estimates of host-cell damage in at least three ways.…”

“…Release of intracellular inorganic cations and anions also correlated well with trypan blue staining (G. T. Chang and J. W. Moulder, manuscript in preparation). DISCUSSION Injury to host cells is a frequent consequence of the ingestion of both C. psittaci and C. trachomatis (1,2,5,9,12,13,20,24,25,26,27,30). Understanding of the damaging effect of the ingestion of chlamydial cells and of the factors controlling the nature and extent of the damage is a prerequisite to elucidation of the pathogenesis of chiamydial diseases.…”

The intracellular life of Chlamydia psittaci: how do the bacteria interact with the host cell?

“…In early studies monitoring protein incorporation with radiolabeled amino acids, Stokes [91] proposed that the inclusion membrane might be made from either precursors already present in the host cell at the time of infection, or pre-existing membranous structures. According to this study, in the ¢rst 20 h post infection there were no marked changes in the synthesis of new membranous structures by the host cell or in the stability of the membranes already present at the time of infection.…”

The intracellular life ofChlamydia psittaci: how do the bacteria interact with the host cell?

“…In early studies monitoring protein incorporation with radiolabeled amino acids, Stokes [91]proposed that the inclusion membrane might be made from either precursors already present in the host cell at the time of infection, or pre‐existing membranous structures. According to this study, in the first 20 h post infection there were no marked changes in the synthesis of new membranous structures by the host cell or in the stability of the membranes already present at the time of infection.…”