[HTML][HTML] The Effects of Methionine Acquisition and Synthesis on Streptococcus Pneumoniae Growth and Virulence

S Basavanna, S Chimalapati, A Maqbool, B Rubbo… - PLoS …, 2013 - journals.plos.org
S Basavanna, S Chimalapati, A Maqbool, B Rubbo, J Yuste, RJ Wilson, A Hosie…
PLoS One, 2013journals.plos.org
Bacterial pathogens need to acquire nutrients from the host, but for many nutrients their
importance during infection remain poorly understood. We have investigated the importance
of methionine acquisition and synthesis for Streptococcus pneumoniae growth and virulence
using strains with gene deletions affecting a putative methionine ABC transporter lipoprotein
(Sp_0149, metQ) and/or methionine biosynthesis enzymes (Sp_0585-Sp_0586, metE and
metF). Immunoblot analysis confirmed MetQ was a lipoprotein and present in all S …
Bacterial pathogens need to acquire nutrients from the host, but for many nutrients their importance during infection remain poorly understood. We have investigated the importance of methionine acquisition and synthesis for Streptococcus pneumoniae growth and virulence using strains with gene deletions affecting a putative methionine ABC transporter lipoprotein (Sp_0149, metQ) and/or methionine biosynthesis enzymes (Sp_0585 - Sp_0586, metE and metF). Immunoblot analysis confirmed MetQ was a lipoprotein and present in all S. pneumoniae strains investigated. However, vaccination with MetQ did not prevent fatal S. pneumoniae infection in mice despite stimulating a strong specific IgG response. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry demonstrated that MetQ has both a high affinity and specificity for L-methionine with a KD of ∼25 nM, and a ΔmetQ strain had reduced uptake of C14-methionine. Growth of the ΔmetQmetEF strain was greatly impaired in chemically defined medium containing low concentrations of methionine and in blood but was partially restored by addition of high concentrations of exogenous methionine. Mixed infection models showed no attenuation of the ΔmetQ, ΔmetEF and ΔmetQmetEF strains in their ability to colonise the mouse nasopharnyx. In a mouse model of systemic infection although significant infection was established in all mice, there were reduced spleen bacterial CFU after infection with the ΔmetQmetEF strain compared to the wild-type strain. These data demonstrate that Sp_0149 encodes a high affinity methionine ABC transporter lipoprotein and that Sp_0585 – Sp_0586 are likely to be required for methionine synthesis. Although Sp_0149 and Sp_0585-Sp_0586 make a contribution towards full virulence, neither was essential for S. pneumoniae survival during infection.
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