Protein and DNA synthesis demonstrated in cell-free Ehrlichia chaffeensis organisms in axenic medium

• Published in: Scientific reports Vol. 8; no. 1; pp. 9293 - 12
• Main Authors: Eedunuri, Vijay K., Zhang, Yuntao, Cheng, Chuanmin, Chen, Li, Liu, Huitao, Omsland, Anders, Boyle, Dan, Ganta, Roman R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18-06-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 13; 13/106; 14; 14/1; 14/28; 14/63; 38; 38/1; 38/71; 631/326/41/2537; 631/326/41/88; Acetic acid; Amino acids; ATP; Centrifugation; Deoxyribonucleic acid; DNA; DNA biosynthesis; Ehrlichia chaffeensis; Ehrlichiosis; Energy sources; Humanities and Social Sciences; Ketoglutaric acid; Monocytes; multidisciplinary; Nucleotides; Protein biosynthesis; Protein synthesis; Proteins; Replication; Science; Science (multidisciplinary); Sodium acetate
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-27574-z

Ehrlichia chaffeensis
, a tick-transmitted rickettsial bacterium, is the causative agent of human monocytic ehrlichiosis. Biochemical characterization of this and other related Rickettsiales remains a major challenge, as they require a host cell for their replication. We investigated the use of an axenic medium for
E
.
chaffeensis
growth, assessed by protein and DNA synthesis, in the absence of a host cell.
E
.
chaffeensis
organisms harvested from
in vitro
cultures grown in a vertebrate cell line were fractionated into infectious dense-core cells (DC) and the non-infectious replicating form, known as reticulate cells (RC) by renografin density gradient centrifugation and incubated in the axenic medium containing amino acids, nucleotides, and different energy sources. Bacterial protein and DNA synthesis were observed in RCs in response to glucose-6-phosphate, although adenosine triphosphate, alpha-ketoglutarate or sodium acetate supported protein synthesis. The biosynthetic activity could not be detected in DCs in the axenic medium. While the data demonstrate
de novo
protein and DNA synthesis under axenic conditions for
E
.
chaffeensis
RCs, additional modifications are required in order to establish conditions that support bacterial replication, and transition to DCs.