Biology subjects

Bou Khalil, J. Y.

Publications and source records attributed to Bou Khalil, J. Y..

4 recordsLinked to original sources

bioRxiv2021

Adapted protocol for Saccharibacteria co-cultivation: two new members join the club of Candidate Phyla radiation

The growing application of metagenomics to different ecological and microbiome niches in recent years has enhanced our knowledge of global microbial biodiversity. Among these abundant and widespread microbes, Candidate Phyla Radiation or CPR have been recognised as representing a large proportion of the microbial kingdom (> 26%). CPR are characterised by their obligate symbiotic or exo-parasitic activity with other microbial hosts, mainly bacteria. Currently, isolating CPR is still considered challenging for microbiologists. The idea of this study was to develop an adapted protocol for the co-culture of CPR with a suitable bacterial host. Based on various sputa, we tried to purify CPR (Saccharibacteria members) and to cultivate them with pure hosts. This protocol was monitored by real-time PCR quantification using a specific system for Saccharibacteria designed in this study, as well as by electron microscopy and sequencing. We succeeded in co-culturing and sequencing a complete genome of two new Saccharibacteria species: Candidatus Minimicrobia naudis and Candidatus Minimicrobia vallesae. In addition, we noticed a decrease in the Ct number of Saccharibacteria, and a significant multiplication through their physical association with Schaalia odontolytica strains in the enriched medium that we developed. This work may help bridge gaps in the genomic database by providing new CPR members and, in the future, their currently unknown characteristics may be revealed. IMPORTANCEIn this study, the first real-time PCR system has been developed. This technique is able to quantify specifically Saccharibacteria members in any sample of interest in order to investigate their prevalence. In addition, another easy, specific and sensitive protocol has been developed to maintain the viability of Saccharibacteria cells in an enriched medium with their bacterial host. The use of this protocol subsequently facilitates studying the phenotypic characteristics of CPR and their physical interactions with bacterial species, as well as the sequencing of new genomes to improve the current database.

microbiology↗

bioRxiv2020

High speed large scale automated isolation of SARS-CoV-2 from clinical samples using miniaturized co-culture coupled with high content screening

SARS-CoV-2, a novel coronavirus infecting humans, is responsible for the current COVID-19 global pandemic. If several strains could be isolated worldwide, especially for in-vitro drug susceptibility testing and vaccine development, few laboratories routinely isolate SARS-CoV-2. This is due to the fact that the current co-culture strategy is highly time consuming and requires working in a biosafety level 3 laboratory. In this work, we present a new strategy based on high content screening automated microscopy (HCS) allowing large scale isolation of SARS-CoV-2 from clinical samples in 1 week. A randomized panel of 104 samples, including 72 tested positive by RT-PCR and 32 tested negative, were processed with our HCS procedure and were compared to the classical isolation procedure. Isolation rate was 43 % with both strategies on RT-PCR positive samples, and was correlated with the initial RNA viral load in the samples, where we obtained a positivity threshold of 27 Ct. Co-culture delays were shorter with HCS strategy, where 80 % of the positive samples were recovered by the third day of co-culture, as compared to only 25 % with the classic strategy. Moreover, only the HCS strategy allowed us to recover all the positive elements after 1 week of co-culture. This system allows rapid and automated screening of clinical samples with minimal operator work load, thus reducing the risks of contamination.

microbiology↗

bioRxiv2020

Advantages and limits of metagenomic assembly and binning of a giant virus

Giant viruses have large genomes, often within the size range of cellular organisms. This distinguishes them from most other viruses and demands additional effort for the successful recovery of their genomes from environmental sequence data. Here we tested the performance of genome-resolved metagenomics on a recently isolated giant virus, Fadolivirus, by spiking it into an environmental sample from which two other giant viruses were isolated. At high spike-in levels, metagenome assembly and binning led to the successful genomic recovery of Fadolivirus from the sample. A complementary survey of viral hallmark genes indicated the presence of other giant viruses in the sample matrix, but did not detect the two isolated from this sample. Our results indicate that genome-resolved metagenomics is a valid approach for the recovery of near-complete giant virus genomes given that sufficient clonal particles are present. Our data also underline that a vast majority of giant viruses remain currently undetected, even in an era of terabase-scale metagenomics.

microbiology↗

bioRxiv2019

High Content Screening, a reliable system for Coxiella burnetii isolation from clinical samples

Q fever, caused by Coxiella burnetii, is a worldwide zoonotic disease that may cause severe forms in humans and requires a specific and prolonged antibiotic treatment. Although the current serological and molecular detection tools enable a reliable diagnosis of the disease, culture of C. burnetii strains is mandatory to evaluate their antibiotic susceptibility and sequence their genome in order to optimize patient management and epidemiological studies. However, cultivating this fastidious microorganism is difficult and restricted to reference centers as it requires biosafety-level 3 laboratories and relies on cell culture performed by experienced technicians. In addition, the culture yield is low, which results in a small number of isolates being available. In this work, we developed a novel high content screening (HCS) isolation strategy based on optimized high-throughput cell culture and automated microscopic detection of infected cells with specifically-designed algorithms targeting cytopathic effects. This method was more efficient than the shell-vial assay when applied to both frozen specimens (7 isolates recovered by HCS only, sensitivity 91% vs 78% for shell-vial) and fresh samples (1 additional isolate using HCS, sensitivity 7% vs 5% for shell-vial). In addition, detecting positive cultures by an automated microscope reduced the need for expertise and saved 24% of technician working time. Application of HCS to antibiotic susceptibility testing of 12 strains demonstrated that it was as efficient as the standard procedure that combines shell-vial culture and quantitative PCR. Overall, this high-throughput HCS system paves the way to the development of improved cell culture isolation of human viruses.

microbiology↗