Two Novel Point Mutations in Clinical Staphylococcus aureus Reduce Linezolid Susceptibility and Switch on the Stringent Response to Promote Persistent Infection
A) Results of microarray transcriptional analysis of JKD6229 (SCV) compared to JKD6210 (MRSA). Up-regulated genes (in red) are differentially up-regulated in JKD6229 compared to the parent strain JKD6210, and the down-regulated genes (in green) are differentially down-regulated in JKD6229 compared to JKD6210. The heat map analysis highlights the proportion of each cluster of orthologous groups (COG) functional group  that is differentially regulated in the array analysis. This clearly demonstrates global transcriptional changes in the SCV strain, affecting genes from all COG groups. J is associated with translation, ribosomal structure and biogenesis; K is related to transcription; L is related to replication, recombination and repair; B is related to chromatin structure and dynamics; D is related to cell cycle control, cell division, chromosome partitioning; V is related to defence mechanisms, T is related to signal transduction mechanism; M is related to cell wall, membrane and envelope biogenesis; N is related to cell motility; U is related to intracellular trafficking, secretion, and vesicular transport; O is related to posttranslational modification, protein turnover, chaperones; C is related to energy production and conversion; G is related to carbohydrate transport and metabolism; E is related to amino acid transport and metabolism; F is related to nucleotide transport and metabolism; H is related to coenzyme transport and metabolism; I is related to lipid transport and metabolism; P is related to inorganic ion transport and metabolism; Q is related to secondary metabolites biosynthesis, transport and catabolism; R and S are function unknown or general function prediction only categories. B) Anti-capsule type 5 immunoblot of serial dilutions of crude capsule extracts from JKD6210, JKD6229, and control strains Newman (Cap5 positive) and P1 (Cap8 positive), demonstrating a marked increase in capsule production in the SCV strain JKD6229, consistent with the microarray transcriptional profiles.