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Efficient replication in vivo is essential for a microparasite to colonize its host and the understanding of the molecular mechanisms by which microbial pathogens grow within host tissues can lead to the discovery of novel therapies to treat infection. Here we present evidence that the foodborne bacterial pathogen Listeria monocytogenes, a facultative intracellular parasite, exploits hexose phosphates (HP) from the host cell as a source of carbon and energy to fuel fast intracellular growth. HP uptake is mediated by Hpt, a bacterial homolog of the mammalian translocase that transports glucose-6-phosphate from the cytosol into the endoplasmic reticulum in the final step of gluconeogenesis and glycogenolysis. Expression of the Hpt permease is tightly controlled by the central virulence regulator PrfA, which upon entry into host cells induces a set of virulence factors required for listerial intracellular parasitism. Loss of Hpt resulted in impaired listerial intracytosolic proliferation and attenuated virulence in mice. Hpt is the first virulence factor to be identified as specifically involved in the replication phase of a facultative intracellular pathogen. It is also a clear example of how adaptation to intracellular parasitism by microbial pathogens involves mimicry of physiological mechanisms of their eukaryotic host cells.

Author(s): Mariela Scortti [1, 2, 3, 4]; Lizeth Lacharme-Lora [1, 3, 4]; Martin Wagner [2, 4, 5]; Isabel Chico-Calero [2]; Patrizia Losito [1]; Jose A Vazquez-Boland (corresponding author) [1, 2, [...]

The human milk microbiota is a complex and diverse ecosystem that seems to play a relevant role in the mother-to-infant transmission of microorganisms during early life. Bacteria present in human milk may arise from different sources, and recent studies suggest that at least some of them may be originally present in the maternal digestive tract and may reach the mammary gland through an endogenous route during pregnancy and lactation. The objective of this work was to elucidate whether some lactic acid bacteria are able to translocate and colonize the mammary gland and milk. For this purpose, two lactic acid bacteria strains (Lactococcus lactis MG1614 and Lactobacillus salivarius PS2) were transformed with a plasmid containing the lux genes; subsequently, the transformed strains were orally administered to pregnant mice. The murine model allowed the visualization, isolation, and Polymerase Chain Reaction (PCR)-detection of the transformed bacteria in different body locations, including mammary tissue and milk, reinforcing the hypothesis that physiological translocation of maternal bacteria during pregnancy and lactation may contribute to the composition of the mammary and milk microbiota. [ABSTRACT FROM AUTHOR]

Many fluorescent sensors are currently available for in vitro bio-physiological microscopic imaging. The ability to label cells in living animals with these fluorescent sensors would help translate some of these assays into in vivo applications. To achieve this goal, the first step is to establish a method for selectively labeling target cells with exogenous fluorophores. Here we tested whether the HaloTag® protein tagging system provides specific labeling of xenograft tumors in living animals. After systemic delivery of fluorophore-conjugated ligands, we performed whole animal planar fluorescent imaging to determine uptake in tag-expressing HCT116 xenografts. Our results demonstrate that HaloTag ligands containing red or near-infrared fluorophores have enhanced tumor uptake and are suitable for non-invasive in vivo imaging. Our proof-of-concept results establish feasibility for using HaloTag technology for bio-physiological imaging in living animals.

Many fluorescent sensors are currently available for in vitro bio-physiological microscopic imaging. The ability to label cells in living animals with these fluorescent sensors would help translate some of these assays into in vivo applications. To achieve this goal, the first step is to establish a method for selectively labeling target cells with exogenous fluorophores. Here we tested whether the HaloTag® protein tagging system provides specific labeling of xenograft tumors in living animals. After systemic delivery of fluorophore-conjugated ligands, we performed whole animal planar fluorescent imaging to determine uptake in tag-expressing HCT116 xenografts. Our results demonstrate that HaloTag ligands containing red or near-infrared fluorophores have enhanced tumor uptake and are suitable for non-invasive in vivo imaging. Our proof-of-concept results establish feasibility for using HaloTag technology for bio-physiological imaging in living animals.