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Knowledge on the proteome level about the adaptation of pathogenic mycobacteria to the environment in their natural hosts is limited. Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease, a chronic and incurable granulomatous enteritis of ruminants, and has been suggested to be a putative aetiological agent of Crohn's disease in humans. Using a comprehensive LC-MS-MS and 2D difference gel electrophoresis (DIGE) approach, we compared the protein profiles of clinical strains of MAP prepared from the gastrointestinal tract of diseased cows with the protein profiles of the same strains after they were grown in vitro. LC-MS-MS analyses revealed that the principal enzymes for the central carbon metabolic pathways, including glycolysis, gluconeogenesis, the tricaboxylic acid cycle and the pentose phosphate pathway, were present under both conditions. Moreover, a broad spectrum of enzymes for β-oxidation of lipids, nine of which have been shown to be necessary for mycobacterial growth on cholesterol, were detected in vivo and in vitro. Using 2D-DIGE we found increased levels of several key enzymes that indicated adaptation of MAP to the host. Among these, FadE5, FadE25 and AdhB indicated that cholesterol is used as a carbon source in the bovine intestinal mucosa; the respiratory enzymes AtpA, NuoG and SdhA suggested increased respiration during infection. Furthermore higher levels of the pentose phosphate pathway enzymes Gnd2, Zwf and Tal as well as of KatG, SodA and GroEL indicated a vigorous stress response of MAP in vivo. In conclusion, our results provide novel insights into the metabolic adaptation of a pathogenic mycobacterium in its natural host.

Bovine Johne's disease (paratuberculosis), caused by Mycobacterium avium subspecies paratuberculosis, poses a significant economic problem to the beef and dairy industry worldwide. Despite its relevance, however, pathogenesis of Johne's disease is still only partially resolved. Since mycobacterial membrane proteins expressed during infection are likely to play an important role in pathogenesis, membrane-enriched fractions, namely mucosa-derived membranes (MDM) and culture-derived membranes (CDM), of M. avium subsp. paratuberculosis from three cows with clinical paratuberculosis were investigated. An initial analysis by 2D difference gel electrophoresis (2D DIGE) and MALDI-TOF-MS analysis revealed four differentially expressed proteins with only one predicted membrane protein. Due to this limited outcome, membrane preparations were subjected to a tube–gel trypsin digestion and investigated by using nanoflow-liquid-chromatography-coupled tandem MS. Based on this approach a total of 212 proteins were detected in MDM including 32 proteins of bovine origin; 275 proteins were detected in CDM; 59 % of MDM and CDM proteins were predicted to be membrane-associated. A total of 130 of the proteins were detected in both MDM and CDM and 48 predicted membrane proteins were detected in MDM from at least two cows. Four of these proteins were not detected in CDM, implying differential expression in the host. All membrane-associated proteins, especially the four identified as being differentially expressed, might be relevant targets for further analyses into the pathogenesis of bovine paratuberculosis.

Mycobacterium (M.) avium subsp. paratuberculosis – the causative agent of paratuberculosis (Johne's disease) – affects domestic and wild ruminants worldwide. Recently, different typing techniques have been combined to provide sufficient discriminatory power for the differentiation of isolates and for epidemiological studies. In order to challenge the reliability of this approach the stability of different M. avium subsp. paratuberculosis genotypes determined after primary isolation was investigated after sub-cultivation on six different media (A), twelve in vitro passages (B), or a singular in vivo passage (C). In addition, different isolates from a single animal or herd were investigated (D). Sub-cultures of type- and reference strains, re-isolated inoculation strain after in vivo passage, and 23 field isolates were genotyped by mycobacterial interspersed repetitive unit-variable-number of tandem-repeat (MIRU-VNTR)-, short-sequence-repeat (SSR)-, and IS900-based restriction-fragment length-polymorphism (IS900-RFLP)-analyses and compared with initial genotypes. MIRU-VNTR-alleles (at loci 292, X3, 25, 47, 7, and 32) were stable after in vitro cultivations and after animal passage. Results of SSR analysis at Locus 1 with 7G nucleotides and at Loci 8 and 9 (tri-nucleotides) were also stable. At Locus 2 9G repeats changed into 10G after goat passage. After in vitro subculture (A + B) but not after animal passage (C) IS900-RFLP-typing revealed changes of BstEII-patterns for 3 of 23 strains (including ATCC 19698). Multiple isolates from individual animals or from a single cattle herd with natural infection (D) which exhibited identical IS900-RFLP- and MIRU-VNTR- genotypes, showed different G repeat numbers at SSR locus 2. This implies strand slippage events during chromosomal duplication of bacteria in the course of bacterial spreading within hosts and herds. Consequently, SSR-Locus 2 is not suitable as genome marker for epidemiological studies.