Abstract:Anteiso-branched-chain fatty acids (BCFA) represent the dominant group of membrane fatty acids and have been established as crucial determinants in resistance against environmental stresses in Listeria monocytogenes, a facultative intracellular pathogen. Here, we investigate the role of anteiso-BCFA in L. monocytogenes virulence by using mutants deficient in branched-chain alpha-keto acid dehydrogenase (BKD), an enzyme complex involved in the synthesis of BCFA. In tissue culture models of infection, anteiso-BC… Show more
“…Interestingly, the absence of C15:0 anteiso branched chain fatty acid in the M1⌬STP mutant (Table 1) is attributed to the 4 -10-fold down-regulation of the fabH gene (SPy1754), which is involved in the branched chain fatty acid synthesis (44). The down-regulation of the fabH/ SPy1754 in M1⌬STP and corresponding absence of the C15:0 anteiso branched chain fatty acid (44) corroborate with the attenuation of virulence, as was also observed in S. aureus (45) and L. monocytogenes (40). Further, the undetected C17:0 cyclopropane fatty acid, which is responsible for conferring acid tolerance to bacteria by altering the membrane rigidity and fluidity (46), may play an indirect role in reduced survival of the M1⌬STP mutant within the host, especially while encountering an unfavorable intracellular environment.…”
Section: Discussionmentioning
confidence: 48%
“…The role of lipid biosynthesis in virulence regulation has been studied for S. pneumoniae (38), S. aureus (39), and L. monocytogenes (40) but not for GAS. Like S. pneumoniae, the FAS-II operon in the M1SF370 GAS strain is constituted by SPy1743 to SPy1755.…”
Background: Unlike for eukaryote-type serine/threonine kinase of group A Streptococcus (GAS), significance of its cognate serine/threonine phosphatase (SP-STP) remains elusive. Results: SP-STP is crucial for GAS pathophysiology. Conclusion: SP-STP is not essential for GAS survival, but its optimal concentration is critical for cognately maintained homeostasis within GAS. Significance: This work opens up avenues to understand the role of secretory SP-STP as an important virulence determinant in the host.
“…Interestingly, the absence of C15:0 anteiso branched chain fatty acid in the M1⌬STP mutant (Table 1) is attributed to the 4 -10-fold down-regulation of the fabH gene (SPy1754), which is involved in the branched chain fatty acid synthesis (44). The down-regulation of the fabH/ SPy1754 in M1⌬STP and corresponding absence of the C15:0 anteiso branched chain fatty acid (44) corroborate with the attenuation of virulence, as was also observed in S. aureus (45) and L. monocytogenes (40). Further, the undetected C17:0 cyclopropane fatty acid, which is responsible for conferring acid tolerance to bacteria by altering the membrane rigidity and fluidity (46), may play an indirect role in reduced survival of the M1⌬STP mutant within the host, especially while encountering an unfavorable intracellular environment.…”
Section: Discussionmentioning
confidence: 48%
“…The role of lipid biosynthesis in virulence regulation has been studied for S. pneumoniae (38), S. aureus (39), and L. monocytogenes (40) but not for GAS. Like S. pneumoniae, the FAS-II operon in the M1SF370 GAS strain is constituted by SPy1743 to SPy1755.…”
Background: Unlike for eukaryote-type serine/threonine kinase of group A Streptococcus (GAS), significance of its cognate serine/threonine phosphatase (SP-STP) remains elusive. Results: SP-STP is crucial for GAS pathophysiology. Conclusion: SP-STP is not essential for GAS survival, but its optimal concentration is critical for cognately maintained homeostasis within GAS. Significance: This work opens up avenues to understand the role of secretory SP-STP as an important virulence determinant in the host.
“…In the present study, we demonstrate that genetic disruption or exposure to FA precursors that lead to alterations in FA composition significantly compromise stress resistance and intracellular fitness. Disruption of the synthesis of BCFAs, the dominant class of membrane FA, through genetic mutation, causes decreases in membrane fluidity (14,27), in vitro growth defects at low temperature and low pH (22,62), and reduced intracellular growth and infection in vivo (50). Here, we establish a specific requirement for BCFAs in resistance against surface stresses and phagosomal killing.…”
Section: Discussionmentioning
confidence: 95%
“…Second, we assayed for LLO production using bacteria grown with both butyrate and 2MB supplementation to test a potential signaling role for butyrate. Supplementation with 2MB (5 mM) by itself causes no changes in LLO production in WT bacteria (50). Supplementation with 25 mM 2MB in HEPES-buffered BHI completely restored anteiso-BCFA content in bacteria grown with 250 mM butyrate (Fig.…”
Section: Figmentioning
confidence: 99%
“…However, after transducing the insertion into a clean isogenic wild-type background, we demonstrated with two independent transductants that deficiency in BKD resulted in strong attenuation in both tissue culture and mouse infection models. The BKD insertion mutants also exhibited a significant defect in production of listeriolysin O, the cytolysin required for phagosomal escape (50).…”
dFatty acids (FAs) are the major structural component of cellular membranes, which provide a physical and chemical barrier that insulates intracellular reactions from environmental fluctuations. The native composition of membrane FAs establishes the topological and chemical parameters for membrane-associated functions and is therefore modulated diligently by microorganisms especially in response to environmental stresses. However, the consequences of altered FA composition during host-pathogen interactions are poorly understood. The food-borne pathogen Listeria monocytogenes contains mostly saturated branched-chain FAs (BCFAs), which support growth at low pH and low temperature. In this study, we show that anteiso-BCFAs enhance bacterial resistance against phagosomal killing in macrophages. Specifically, BCFAs protect against antimicrobial peptides and peptidoglycan hydrolases, two classes of phagosome antimicrobial defense mechanisms. In addition, the production of the critical virulence factor, listeriolysin O, was compromised by FA modulation, suggesting that FAs play a key role in virulence regulation. In summary, our results emphasize the significance of FA metabolism, not only in bacterial virulence regulation but also in membrane barrier function by providing resistance against host antimicrobial stress.
Listeria monocytogenes is a psychrotolerant food borne pathogen, responsible for the high fatality disease listeriosis, and expensive food product recalls. Branched-chain fatty acids (BCFAs) of the membrane play a critical role in providing appropriate membrane fluidity and optimum membrane biophysics. The fatty acid composition of a BCFA-deficient mutant is characterized by high amounts of straight-chain fatty acids and even-numbered iso fatty acids, in contrast to the parent strain where odd-numbered anteiso fatty acids predominate. The presence of 2-methylbutyrate (C5) stimulated growth of the mutant at 37°C and restored growth at 10°C along with the content of odd-numbered anteiso fatty acids. The C6 branched-chain carboxylic acids 2-ethylbutyrate and 2-methylpentanoate also stimulated growth to a similar extent as 2-methylbutyrate. However, 3-methylpentanoate was ineffective in rescuing growth. 2-ethylbutyrate and 2-methylpentanoate led to novel major fatty acids in the lipid profile of the membrane that were identified as 12-ethyltetradecanoic acid and 12-methylpentadecanoic acid respectively. Membrane anisotropy studies indicated that growth of strain MOR401 in the presence of these precursors increased its membrane fluidity to levels of the wild type. Cells supplemented with 2-methylpentanoate or 2-ethylbutyrate at 10°C shortened the chain length of novel fatty acids, thus showing homeoviscous adaptation. These experiments use the mutant as a tool to modulate the membrane fatty acid compositions through synthetic precursor supplementation, and show how existing enzymes in L. monocytogenes adapt to exhibit non-native activity yielding unique ‘unnatural’ fatty acid molecules, which nevertheless possess the correct biophysical properties for proper membrane function in the BCFA-deficient mutant.
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