Heme uptake inLactobacillus sakeievidenced by a new ECF-like transport system

Abstract

19Lactobacillus sakei is a non-pathogenic lactic acid bacterium and a natural inhabitant of meat 20 ecosystems. Although red meat is a heme-rich environment, L. sakei does not need iron or 21 heme for growth, while possessing a heme-dependent catalase. Iron incorporation into L. 22 sakei from myoglobin and hemoglobin was formerly shown by microscopy and the L. sakei 23 genome reveals a complete equipment for iron and heme transport. Here, we report the 24 characterization of a five-gene cluster (lsa1836-1840) encoding a putative metal iron ABC 25 transporter. Interestingly, this cluster, together with a heme dependent catalase gene, is also 26 conserved in other species from the meat ecosystem. Our bioinformatic analyses revealed 27 that the locus might refer to a complete machinery of an Energy Coupling Factor (ECF) 28 transport system. We quantified in vitro the intracellular heme in wild-type (WT) and in our 29Dlsa1836-1840 deletion mutant using an intracellular heme sensor and ICP-Mass 30 spectrometry for quantifying incorporated 57 Fe heme. We showed that in the WT L. sakei, 31 heme accumulation occurs fast and massively in the presence of hemin, while the deletion 32 mutant was impaired in heme uptake; this ability was restored by in trans complementation. 33 Our results establish the main role of the L. sakei Lsa1836-1840 ECF-like system in heme 34 uptake. This research outcome shed new light on other possible functions of ECF-like 35 systems. 36 37 38 Importance 39Lactobacillus sakei is a non-pathogenic bacterial species exhibiting high fitness in heme rich 40 environments such as meat products, although it does not need iron nor heme for growth. 41Heme capture and utilization capacities are often associated with pathogenic species and are 42 considered as virulence-associated factors in the infected hosts. For these reasons, iron 43 3 acquisition systems have been deeply studied in such species, while for non-pathogenic 44 bacteria the information is scarce. Genomic data revealed that several putative iron 45 transporters are present in the genome of the lactic acid bacterium L. sakei. In this study, we 46 demonstrate that one of them, is an ECF-like ABC transporter with a functional role in heme 47 transport. Such evidence has not yet been brought for an ECF, therefore our study reveals a 48 new class of heme transport system. 49 50 51 7 It was evidenced that ECF transporters constitute a novel family of conserved membrane 126 transporters in prokaryotes, while sharing a similar four domains organization as the ABC 127 transporters. Each ECF displays a pair of cytosolic nucleotide-binding ATPases (the A and A' 128 components also called EcfA and EcfA'), a membrane-embedded substrate-binding protein 129 (the S component or the EcfS), and a transmembrane energy-coupling component (The T 130 component or EcfT). The quadripartite organization has a 1:1:1:1 stoichiometry. Notably, the 131 S component renders ECF mechanistically distinct from ABC transport systems as it is 132 predicted to shuttle within the ...

A Novel Heme Transporter from the Energy Coupling Factor Family Is Vital for Group A Streptococcus Colonization and Infections

“…We also identified homologs of siaFGH next to siaDE-like genes in Streptococcus gordonii and Eggerthella lenta or near iron-dependent repressors in group B streptococcus and Enterococcus faecalis. Finally, while this article was in preparation, a study describing a heme ECF system from Lactobacillus sakei was posted in bioRxiv (57). In silico analyses also suggest that ECF-type transporters mediate siderophore import.…”

Bacteria from the gut influence the host micronutrient status

“…It has been considered for a long time that a few beneficial bacteria, such as members of Lactobacillus genus, do not require iron for their growth (52). Nevertheless, specific systems have been identified in L. plantarum and L. sakei (53,54). Most probably, other systems may exist, and studying these bacteria may reveal new iron absorption pathways.…”