Mohamad Mostafa Koubar

Associate professor
Life & Earth Sciences department - Section V - Nabatiyeh
Speciality: Biology
Specific Speciality: Microbiologie

Teaching 8 Taught Courses
(2014-2015) Biol 111 - Organisation of the living world animal, Reproduction, and Embryology

BS Biochemistry

(2014-2015) Biol 111 - Organisation of the living world animal, Reproduction, and Embryology

BS Earth and life sciences

(2014-2015) Biol 113 - Genetics, human anatomiy and plant reproduction

BS Earth and life sciences

(2014-2015) Biol 113 - Genetics, human anatomiy and plant reproduction

BS Biochemistry

(2014-2015) Biol 273 - General Microbiology

BS Biochemistry

(2014-2015) Biol 325 - Microbiology

BS Earth and life sciences

(2014-2015) Biol 345 - Microbiology Lab

BS Earth and life sciences

(2014-2015) Biol 346 - General Ecology Lab

BS Earth and life sciences

2007 - 2011: Doctorat

Université de Poitiers - France
Aspects moléculaires et cellulaires de la biologie

Très Honorable avec félicitations du jury

2006 - 2007: Master II Recherche

Université de Poitiers - France
Physiologie - Biologie Cellulaire et Moléculaire

2001 - 2006: Maitrise

Université Libanaise - Faculté des Sciences I
Biologie Animale

Publications 3 publications
Mohamad Koubar, Marie-Hélène Rodier, Jacques Frère Involvement of minerals in adherence of Legionella pneumophila to surfaces Curr Microbiol 2013

Legionella pneumophila is the causative agent of 90 % of Legionnaires' disease cases. This bacterium lives naturally in fresh water and can colonize biofilms, which play an important role in the protection of Legionella against environmental stress factors. Relationship between the presence of minerals in water and Legionella adherence to surfaces is not well-known. In this study, we studied influence of minerals on bacterial adherence. For the first time, to our knowledge, this report shows that calcium and magnesium in a less extent, enhances the adherence of Legionella to surfaces compared to the bacteria behavior in distilled water. Treatment with proteinase K of live cells showed that surface proteins do not seem to play a crucial role in bacteria adherence to surfaces. Our results represent a first step in understanding effect of ions on Legionella adherence to surfaces. Such field of research could be helpful to better understand biofilm colonization by this bacterium to improve Legionella risk management in water networks.

Laëtitia Alleron, Arbia Khemiri, Mohamad Koubar, Christian Lacombe, Laurent Coquet, Pascal Cosette, Thierry Jouenne, Jacques Frère VBNC Legionella pneumophila cells are still able to produce virulence proteins Water Research 2013

Legionella pneumophila is the agent responsible for legionellosis. Numerous bacteria, including L. pneumophila, can enter into a viable but not culturable (VBNC) state under unfavorable environmental conditions. In this state, cells are unable to form colonies on standard medium but are still alive. Here we show that VBNC L. pneumophila cells, obtained by monochloramine treatment, were still able to synthesize proteins, some of which are involved in virulence. Protein synthesis was measured using (35)S-labeling and the proteomes of VBNC and culturable cells then compared. This analysis allowed the identification of nine proteins that were accumulated in the VBNC state. Among them, four were involved in virulence, i.e., the macrophage infectivity potentiator protein, the hypothetical protein lpl2247, the ClpP protease proteolytic subunit and the 27 kDa outer membrane protein. Others, i.e., the enoyl reductase, the electron transfer flavoprotein (alpha and beta subunits), the 50S ribosomal proteins (L1 and L25) are involved in metabolic and energy production pathways. However, resuscitation experiments performed with Acanthamoeba castellanii failed, suggesting that the accumulation of virulence factors by VBNC cells is not sufficient to maintain their virulence.

Mohamad Koubar, Marie-Hélène Rodier, Rafael A. Garduno, Jacques Frère Passage through Tetrahymena tropicalis enhances the resistance to stress and the infectivity of Legionella pneumophila FEMS Microbiol Lett 2011

Legionella pneumophila is a gram-negative bacterium prevalent in fresh water which accidentally infects humans and is responsible for the disease called legionellosis. Intracellular growth of L. pneumophila in Tetrahymena is inconsistent; in the species Tetrahymena tropicalis stationary-phase forms (SPFs) of L. pneumophila differentiate into mature intracellular forms (MIFs) without apparent bacterial replication and are expelled from the ciliate as pellets containing numerous MIFS. In the present work, we tested the impact of L. pneumophila passage through T. tropicalis. We observed that MIFs released from T. tropicalis are more resistant to various stresses than SPFs. Under our conditions, MIFs harboured a higher gentamicin resistance, maintained even after 3 months as pellets. Long-term survival essays revealed that MIFs survived better in a nutrient-poor environment than SFPs, as a reduction of only about 3 logs was observed after 4 months in the MIF population, whereas no cultivable SPFs were detected after 3 months in the same medium, corresponding to a loss of about 7 logs. We have also observed that MIFs are significantly more infectious in human pneumocyte cells compared with SPFs. These results strongly suggest a potential role of ciliates in increasing the risk of legionellosis.


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