Intracellular Behaviour of Three Legionella pneumophila Strains within Three Amoeba Strains, Including Willaertia magna C2c Maky

Abstract

Legionella pneumophila is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as Acanthamoeba castellanii. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species support the growth of L. pneumophila. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to possess the ability to eliminate the L. pneumophila strain Paris. Here, we study the intracellular behaviour of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky and compare this strain to A. castellanii and W. magna Z503, which are used as controls. We observe the intracellular growth of strain Lens within W. magna Z503 and A. castellanii at 22 °C and 37 °C. Strain Paris grows within A. castellanii at any temperature, while it only grows at 22 °C within W. magna Z503. Strain Philadelphia proliferates only within A. castellanii at 37 °C. Within W. magna C2c Maky, none of the three legionella strains exhibit intracellular growth. Additionally, the ability of W. magna C2c Maky to decrease the number of internalized L. pneumophila is confirmed. These results support the idea that W. magna C2c Maky possesses unique behaviour in regard to L. pneumophila strains.

Mitigation of Expression of Virulence Genes in Legionella pneumophila Internalized in the Free-Living Amoeba Willaertia magna C2c Maky

“…These results confirm the non-permissiveness observed in W. magna C2c Maky towards L. pneumophila . Unlike A. castellanii , W. magna C2c Maky is able to internalize and digest L. pneumophila by phagocytosis [ 20 , 23 ]. These data suggest that L. pneumophila strains were unable to use their T4SS system to deflect the cellular machinery of W. magna C2c Maky.…”

“…Here, we investigated the expression level by RT-qPCR of 7 genes ( htpX , icmE , lirR , ccmF , gacA , tatB , and lvrE ) that we have shown to be expressed by all three reference strains, L. pneumophila Paris, Philadelphia, and Lens, after co-incubation with two FLA: A. castellanii known to be permissive to the legionella multiplication [ 10 ], and Willaertia magna C2c Maky considered as non-permissive to the legionella multiplication [ 20 ]. We also evaluated transcript levels of these genes in L. pneumophila cultivated alone and harvested at the end of the growth exponential phase corresponding to the end of the replicative phase and the beginning of the virulence phase.…”

Description of Virulent Factors and Horizontal Gene Transfers of Keratitis-Associated Amoeba Acanthamoeba Triangularis by Genome Analysis

“…Free-living amoeba (FLA) food microorganisms, by selective grazing to grow, contribute to the regulation of the environmental microbial population [1,12]. Despite that, some microorganisms named amoeba-resisting microorganisms (ARMs), such as bacteria, fungi, or giant viruses, have the capacity to bypass the internalization in order to survive and multiply in amoebas [13][14][15][16]. The close contact between FLA and ARM promotes horizontal gene transfers, leading to the evolution of microorganisms [17,18].…”

A New Active Substance Derived from Lyzed Willaertia magna C2c Maky Cells to Fight Grapevine Downy Mildew

“…FLA are ubiquitous protozoa that inhabit common aquatic environments [ 13 , 14 ]. FLA are predatory and consume bacteria for their growth [ 15 , 16 , 17 ]. All published papers on FLA deal with the living form of the amoebas and their phagocytic activities.…”