Dr. Gillor has a broad set of research interests that range from the role of antimicrobials in biofilm formation to the diversity of soil bacteria and their role in the ecosystem. What unites this disparate set of topics is the use of molecular and experimental methods to study the processes and patterns of microbial ecology and evolution.
Bacteriocin ecology, evolution and application.(Ghazaryan L., Majeed H., Tonayan L.,)
Bacteriocins comprise a large and functionally diverse family of toxins found in all major lineages of Bacteria. Numerous studies suggest that these potent proteins serve to mediate microbial interactions and may even play a role in maintaining microbial diversity. Colicins, produced by Escherichia coli, have served as a model for many such studies. These high molecular weight toxic proteins specifically target close relatives and kill through one of a variety of mechanisms, including pore formation and nuclease activity. The genes encoding colicins display a unique form of expression, which is confined to stressful conditions and lethal to the producing cell. Although bacteriocins have been studied for over 80 years little is known about the processes that shape their mode of action. Colicin expression in vitro is often accomplished with the addition of DNA damaging agents (publication 13). However, there is some question as to how colicin function in their primary natural environment of enteric bacteria, the mammalian colon (publication 10). Given their lethal nature, it is almost certain that colicin expression has evolved a sophisticated system for repression and expression. We study this unique form of lethal expression, and hope to utilize the answers to detect and control Gram-negative pathogens (publications I, 7, 8, 9, 11 and 20).
Funding: MOST & NIH

Effects of rainfall gradient and landscape sustainability measures on microbial biodiversity and community composition.(Bachar A., Al-Ashhab A.)
How do precipitation gradient, vegetation and grazing affect the biodiversity and community composition of soil Bacteria and Archaea? Microorganisms represent a major component of any ecosystem, however, despite their importance, their role is poorly understood. It has been hypothesized that the combination of precipitation gradient, vegetation cover and grazing creates changes in the soil environment and thus in the composition and diversity of the microbial communities, which may in turn affect soil nutrient cycle and overall productivity. We are conducting a comprehensive long-term study that links spatial and temporal microbial diversity exploring the effects of land sustainability measures on microbial diversity and community composition in five long-term ecological research (LTER) sites positioned along the precipitation gradient in Israel (publication 16). These ecosystems will provide a better understanding of the interactions between the bacterial and plant communities, which can then be applied towards preserving and sustaining natural ecosystems.


Characterization and control of bacterial biofouling(Vanoyan N., Al-Ashhab A.)
What are the mechanisms bacteria use to form biofilm on membranes used for water treatment? The increased demand for freshwater could mainly be met through water reuse by water treatment and seawater desalination using membrane systems. However, the efficiency of the membranes is severely hampered by fouling and in particular by bacterial biofouling followed by a decrease in permeate water flux, and in most cases, salt rejection. We aim to characterize the community composition and diversity bacteria within biofilms developed on membrane during water treatment processes. We study the physiology of the biofilm under typical operating conditions using a model bacterium (publication 14) and in natural populations. These studies could provide the knowledge needed to develop strategies for biofouling control and prevention in various environmental engineered systems (publication 14), such as filters (biological and physical), bioreactors, heat exchangers, and irrigation equipment.
Funding: BMBF & MERC-AID


Monitoring for pathogens in wastewater, irrigated soil, and crops.(Orlofsky E., Benami M., Zough M.)
Contamination of edible crops with human pathogens results in significant morbidity and mortality worldwide. To date, the most common water monitoring practice for fecal contamination in irrigation water relies on culturing fecal indicator bacteria such as Escherichia coli. However, do fecal indicators correlate with levels of disease-causing fecal pathogens in water sources, including treated wastewater effluents? The inability of indicators to accurately predict whether fecal pathogens are present or absent in treated wastewater and the irrigated crops themselves warrants further research that could provide improved produce safety monitoring guidelines to insure that the use of reused wastewater in irrigation is a sustainable and safe practice in arid climates. My lab is engaged in a project that will evaluate if current monitoring techniques that target fecal indicator organisms aiming to accurately predict the presence of fecal pathogens (bacteria, protozoa and viruses) on produce using wastewater irrigated tomatoes as our model plant.
Funding: RCF & BARD

Scientific Publications 2012-2015:

Refereed articles in scientific journals:

1) Bachar A., Soares M.I.M. and Gillor O. (2012). The effect of resource islands on abundance and diversity of bacteria in arid soils. Microbial Ecology. 63:694-700.

2) Pasternak Z., Al-Ashhab A., Gatica J., Gafny R., Avraham S., Frenk S., Minz D., Gillor O. and Jurkevitch E. (2012). Optimization of molecular methods and statistical procedures for forensic fingerprinting of microbial soil communities. International Research Journal of Microbiology. 3: 363-372.

3) Inglis R.F., Bayramoglu B., Gillor O. and Ackermann M. (2013). The role of bacteriocins as selfish genetic elements. Biology Letters. 2013 9: 20121173.

4) Majeed H., Lampert A., Ghazaryan L. and Gillor O. (2013). Dominance of the weak: bacteriocin mediated interactions in bacterial populations. PLoS ONE. 8: e63837.

5) Benami M., Vonshak A., Gross A., Herzberg M., Orlofsky E. and Gillor O. (2013). Assessment of pathogenic bacteria in treated graywater and irrigated soils. Science of the Total Environment. 458:298-302.

6) Orlofsky E., Gillor O., Melli A., Miller W., Wuertz S., Bernstein N. and Shapiro K. (2013). Simultaneous detection of Giardia lambliaandCryptosporidium parvum(oo) cysts in soil using immunomagnetic separation and direct fluorescent antibody staining. Journal of Microbiological Methods. 94: 375-377.

7) Angel R., Pasternak Z., Soares M. I. M., Conrad R. and Gillor O. (2013). Active and total prokaryotic communities in dryland soils. FEMS Microbiology Ecology. 86: 130-8.

8) Pasternak Z., Al-Ashhab A., Gatica J., Gafny R., Avraham S., Minz D., Gillor O. and Jurkevitch E. (2013). Spatial and Temporal Biogeography of Soil Microbial Communities in Arid and Semiarid Regions. 8: e69705.

9) Sklarz M. Y., Zhou M., Ferrando Chavez D. L., Yakirevich A., Gillor O., Gross A. and Soares M. I. M. (2013). Effect of Treated Domestic Wastewater on Soil Physicochemical and Microbiological Properties. Journal of Environmental Quality. 42: 1226-123.

10) Al Ashhab A., Herzberg M., Gillor O. (2014). Biofouling of reverse-osmosis membranes during tertiary wastewater desalination: microbial community composition. Water research, 50: 341-349.

11) Ghazaryan L., Soares I.M., Gillor O. (2014). Auto-regulation of DNA degrading bacteriocins: molecular and ecological aspects. Antonie van Leeuwenhoek, 105 (5): 823-834.

12) Al Ashhab A., Gillor O., Herzberg M. (2014). Biofouling of reverse-osmosis membranes under different shear rates during tertiary wastewater desalination: Microbial community composition. Water research, 67: 86-95.

13) Majeed H., Ghazaryan L., Herzberg M., Gillor O. (2014). Bacteriocin expression in sessile and planktonic populations of Escherichia coli. The Journal of antibiotics, 68: 52–55.

14) Ghazaryan L., Tonoyan L., Al Ashhab A, Soares I.M., Gillor O. (2014). The role of stress in colicin regulation. Archives of microbiology, 196 (11): 753-764.

15) Benami M., Gillor O., Gross A. (2015). The question of pathogen quantification in disinfected graywater. Science of the Total Environment, 506: 496-504.

16) Orlofsky E., Benami M., Gross A., Dutt M., Gillor O. (2015). Rapid MPN-Qpcr Screening for Pathogens in Air, Soil, Water, and Agricultural Produce. Water, Air, & Soil Pollution, 226 (9): 1-10.

17) Orlofsky E., Bernstein N., Sacks M., Vonshak A., Benami M., Kundu A., Maki M., Smith W., Wuertz S., Shapiro K., Gillor O. (2015). Comparable levels of microbial contamination in soil and on tomato crops after drip irrigation with treated wastewater or potable water. Agricultural Ecosystems and Environment, 215: 140-150.

18) Livne-Luzon S., Shemesh H., Gillor O., Ovadia O. (in press 2015). The effect of temporal variation in soil carbon inputs on interspecific plant competition. Journal of Plant Ecology.