A Legionella pneumophila amylase is essential for intracellular replication in human macrophages and amoebae

Abstract

Legionella pneumophila invades protozoa with an “accidental” ability to cause pneumonia upon transmission to humans. To support its nutrition during intracellular residence, L. pneumophila relies on host amino acids as the main source of carbon and energy to feed the TCA cycle. Despite the apparent lack of a requirement for glucose for L. pneumophila growth in vitro and intracellularly, the organism contains multiple amylases, which hydrolyze polysaccharides into glucose monomers. Here we describe one predicted putative amylase, LamB, which is uniquely present only in L. pneumophila and L. steigerwaltii among the ~60 species of Legionella. Our data show that LamB has a strong amylase activity, which is abolished upon substitutions of amino acids that are conserved in the catalytic pocket of amylases. Loss of LamB or expression of catalytically-inactive variants of LamB results in a severe growth defect of L. pneumophila in Acanthamoeba polyphaga and human monocytes-derived macrophages. Importantly, the lamB null mutant is severely attenuated in intra-pulmonary proliferation in the mouse model and is defective in dissemination to the liver and spleen. Our data show an essential role for LamB in intracellular replication of L. pneumophila in amoeba and human macrophages and in virulence in vivo.

Intracellular Presence of Helicobacter pylori and Its Virulence-Associated Genotypes within the Vaginal Yeast of Term Pregnant Women

“…To the best of our knowledge, there is no scientific literature explaining the causes which can influence this phenomenon in H. pylori . However, it has been observed that Legionella pneumophila, a bacterium pathogenic for humans which invades free living amoebas, is capable of modifying its genetic material after gaining access into the protozoa [ 62 ]. This may also be the case when H. pylori enters into yeasts.…”

“…This may also be the case when H. pylori enters into yeasts. It has been reported that the vacA gene shows polymorphism in its medial, intermediate and signal regions, which vary depending on H. pylori strains [ 63 ] and that a defect in one of these regions may be an impediment for the bacterial strain to induce vacuolization in the infected cell [ 33 , 62 , 63 , 64 ]. In this sense, it is worthy to emphasize that the VacA protein plays an important role in the survival of H. pylori in human gastric cells because it alters endosomal traffic and promotes the accumulation of non-functional lysosomes and autophagosomes avoiding the elimination of this pathogen [ 65 , 66 , 67 , 68 ].…”

Nutrition and Bipartite Metabolism of Intracellular Pathogens

“…Why L. pneumophila prefers amino acids over glucose, like most other genera of bacteria studied, is unknown. The answer likely lies within its genome and through better understanding of its evolution with protist hosts [19,20]. Like most driving factors for coevolution, use of amino acids could keep it reliant on its host, limiting growth only when within a host, thus giving L. pneumophila an evolutionary advantage.…”

Molecular Mimicry: a Paradigm of Host-Microbe Coevolution Illustrated by Legionella

“… L. pneumophila GamA is a eukaryotic-like glucoamylase secreted by the T2SS, although the importance of this protein during infection needs to be further elucidated ( 115 ). In contrast, LamB is a Legionella amylase required for intracellular replication and virulence in a mouse model of infection ( 116 ). However, it is not yet clear if this protein is a secreted effector, as LamB does not contain a T2SS secretion signal and experimental validation of secretion by the T4SS was unsuccessful ( 116 ).…”

“…In contrast, LamB is a Legionella amylase required for intracellular replication and virulence in a mouse model of infection ( 116 ). However, it is not yet clear if this protein is a secreted effector, as LamB does not contain a T2SS secretion signal and experimental validation of secretion by the T4SS was unsuccessful ( 116 ). Finally, LamA was recently described as a T4SS-dependent amylase that catalyzes rapid glycogenolysis in amoebae, blocking amoeba encystation and promoting L. pneumophila proliferation ( 117 ).…”