الفهرس 
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Abstract
Water and wastewater may contain a wide variety of bacteria that cause intestinal or extra-intestinal infections. One purpose of drinking water and wastewater treatment is to reduce the number of viable organisms to acceptable levels, and to remove or inactivate all pathogens capable of causing human disease. Despite the success of water treatment and satiation programs in improving public health, sporadic cases and outbreaks of waterborne diseases continue to occur APHA, 2011).1.Water and health:Many people struggle to obtain access to safe water. A clean and treated water supply to each house may be the norm in Europe and North America, but in developing countries, access to both clean water and sanitation are not the rule, and waterborne infections are common. Two and a half billion people have no access to improved sanitation, and more than 1.5 million children die each year -#102;-#114;-#111;-#109; diarrhea diseases (Fenwick, 2006). According to the WHO, the mortality of water associated diseases exceeds 5 million people per year. -#102;-#114;-#111;-#109; these, more than 50% are microbial intestinal infections, with cholera standing out in the first place (Cabral, 2010). Acute microbial diarrheal diseases are major public health problem in developing countries. People affected by diarrheal diseases are those with the lowest financial resources and poorest hygienic facilities. Children under five, primarily in Asian and African countries, are the most affected by microbial diseases transmitted through water (Seas et al., 2000). Microbial waterborne diseases also affect developed countries. In the USA, it has been estimated that each year 560, 000 people suffer -#102;-#114;-#111;-#109; severe waterborne diseases, and 7.1 million suffer -#102;-#114;-#111;-#109; a mild to moderate infections, resulting in estimated 12, 000 deaths a year (Medema et al., 2003). br In general terms, the greatest microbial risks are associated with ingestion of water that is contaminated with human or animal feces (Cabral, 2010). Waste water discharges in fresh waters and coastal seawaters are the major sources of fecal microorganism, including pathogens (Grabow, 1996; George et al., 2001; Fenwick, 2006 and WHO, 2008). br According to World Health Association, 1.1 billion people in low and middle income countries lack access to safe water for drinking use (WHO, 2004). When humans drink polluted water, it often has serious effects on their health resulting in the spread of many diseases. Water pollution can also make water unsuited for the desired use (Naheed et al., 2005). The unscientific disposal of the wastewater has caused immense environmental problems not only to the aquatic environment but also to human beings worldwide. br In Egypt, water-related diseases are endemic accounting for 90.000 deaths each year (UNEP, 2000). Outbreaks of diseases such as cholera, typhoid and infectious hepatitis have occurred in several provinces because of drinking water pollution. For instance, 10% of the rural population in 1995 was affected by diseases result of contamination of surface water with human waste (GOE, 1997). The contamination of those surface and ground waters could also affect the food chain causing deadly intestinal diseases or poisoning. The poor treatment of wastewater is the main cause of the high nitrates concentration, turbidity, nitrite and ammonia. Also, the poor treatment is the main cause of microorganisms, viruses (Echo, Norwalk and Hepatitis), protozoa, fecal coliforms, and fecal streptococci in the surrounding area. All of these have a direct effect on human health, causing diarrhea, gastroenteritis problems, respiratory disease, aseptic meningitis, jaundice, liver failure and typhoid fever (Melad, 2002). br The problem of water pollution is also growing at an alarming rate; the phenomenal increase in country’s population has brought unprecedented pressure on safe drinking water. Waterborne diseases account for 20 to 30% of all hospital cases and 60% infant deaths (Government of Pakistan, 2000). In Pakistan, 72 % population lives in rural area. More of them have not the availability of good quality drinking water. So due to polluted water the people of villages have a many diseases like typhoid, stomach problems, kidney problems, food poisoning and skin problem (Naheed et al., 2005). br Wastewater discharges may contain pathogens, carcinogenic substances, and chemical substances which may cause adverse environmental impact such as changes in aquatic habitats and species composition, decrease in biodiversity impaired use of recreational waters and shellfish harvesting areas and contaminated drinking water (CCME, 2006). All of these impacts lead to a less valuable environment, poor health, a less prosperous economy, and ultimately, a diminished quality of life. br In Egypt, it has been reported several disease conditions including hypertension, hepathomegaly, dermatitis and chromosomal aberrations caused by agriculture wastewater (pesticide) (Amer, 1994). Pesticide exposure has been associated with elevated cancer risks (Horrigan et al., 2002). br Water is essential to sustain life, and satisfactory supply must be available to consumer. No source of water that intended for human consumption can be assumed to be free -#102;-#114;-#111;-#109; pollution. Polluted water is an important vehicle for the spread of diseases. It has been estimated that 50.000 people die daily in the world as a result of water related diseases (Schalrkamp, 1990). br Water pollution is one of the principal environmental and public health problems Egyptian Nile River are facing (Anwar, 2003). Pollution in the Nile River system (main stem Nile, drains and canals) has increased in the last few decades because of increases in population; several new irrigated agriculture projects, and other activities along the Nile. Not only developed countries have been affected by environmental problems, but also, the developing nations suffer the impact of pollution due to disorded economic growth associated with the exploration of virgin natural sources (Listori, 1990). br The water availability has always been of great importance for life and for every living organism. It has a life-sustaining role in welfare and growth of mankind. All life on the earth is dependent on water and so does many economic activities. Every human individual require about 2 liters of clean drinking water per day and this amount reaches to almost 12 millions m3 per day for the world population (Yassi et al., 2001). About 69% of fresh water worldwide is used for domestic purpose that is for drinking, cooking sanitation, 22% in industries, 8% for irrigation. The quality of water is important to the health, social and economic well being of people. It is important to test the suitability of the quality of water for its use as drinking water. Water that looks drinkable can contain bacterial contamination, which are not visible to naked eye and cannot be detected by smell, taste and sight. Variety of bacteria may be present in water even which looks clear and tasted well may not necessarily be safe to drink. Due to anthropogenic interventions the water is getting polluted and thus causing negative effects in human lives and in natural equilibrium. The problems in water sources have become one of the primary problems of human lives. Due to the water borne diseases which result -#102;-#114;-#111;-#109; inadequate water supply, hygiene and sanitation, around 4 million people suffer -#102;-#114;-#111;-#109; water borne diseases and 2.2 million people die -#102;-#114;-#111;-#109; these diseases every year (UNICEF-WHO, 2008). The problem is even severe in developing countries -#119;-#104;-#101;-#114;-#101; generally the drinking water is untreated. The infants are the most vulnerable targets of these diseases. Bacteria constitute one of the major contaminants of water (Suthar et al., 2009). They have been reported to persist even in the extreme environmental conditions and oligotrophic conditions (Sigee, 2005). Moreover, many of the bacterial species have the ability to make resistant survival structures. br Majority of bacteria inhabiting the drinking water belong to the classes Alpha- Proteobacteria such as Sphingomonas, Hyphmicrobium and Pedomicrobium and Beta-proteobacteria such as Dechlormonas, Aquaspirillium. Gamm-aproteobacteria such as Legionella and Mycobacteria were also found in drinking water (Domingo et al., 2003). Additionally, the coliform bacterial group may occur in water due to fecalcontamination that is discharge of faeces by human and other animals (Kaspar et al., 1990). Coliform includes the member’s of Enterobacteriaceae example Escherichia coli, Enterobacter aerogenes, Salmonella and Klebsiella spp. These enteropathogenic bacteria in water are responsible for a variety of diseases like cholera, typhoid, dysenteries, bacillary dysentery, etc. in human and livestock (Ashbolt, 2004). br 2. Causes of water pollution br The Nile river is divided into seven segments according to the geographical features, the administrative boundaries and the human activities, Cairo segment is considered the most important one because it represents the major cluster of drinking water treatment plants and the more populated area. Changes in water quality are expected to be more pronounced as the river penetrates density populated urban areas and various industrial regions. Man frequently destroys the stream’s capacity for natural self purification through excessive additions of domestic sewage and industrial wastes. Therefore, a wide variety of pathogens may be transmitted by fecally polluted water (UNEP, 1991). br Due to huge municipal, industrial, agricultural are discharged without proper treatment in River Nile waterborne diseases are rapidly spreading in the Egyptian society (Abou-Zeid, 1996). br 3. Microbiological quality of drinking water br The provision of a safe supply of drinking water depends up on use of either protected high quality ground water or a property selected and operated series of treatment capable to reduce pathogens and other contaminants to negligible health risk. -#119;-#104;-#101;-#114;-#101; the infectious diseases caused by pathogenic bacteria, viruses and parasites are the most common and widespread health risk associated with drinking water. The elimination of all these agents -#102;-#114;-#111;-#109; drinking water has apriority so the Egyptian standard (2007) for drinking water declared that potable water must be free -#102;-#114;-#111;-#109; total and fecal coliforms as well as Streptococci, in addition total bacterial counts must be less than 50 CFU/ml. br Payment et al. (1997) in an epidemiological study confirmed that tap water is a significance source of gastrointestinal illnesses (14 - 40 %) even if it meets all current drinking water quality criteria. Many studies showed that, coliforms- free potable water may not necessary are free of microbial pathogens or viruses (Grabow et al., 1998). Drinking water has been shown to be a source of Aeromonas, their presence are attributable to ineffective disinfection at the treatment plant, or a result of after growth within the distribution system (Gavriel et al., 1998). br Schulbert (1991) confirmed the presence of Aeromonas hydrophila in drinking water along with other enteropathogens (e.g. salamonellas, enteropathogenic E. coli) reflecting contamination of the environment. Townsend (1992) found significance difference between salmonellae count and bacterial indicator organisms. Samhan (1998) assumed that salmonellae, Vibrio cholera and yeasts must be checked in parallel with other indicators. Thus the search for new indicators of pollution is very important to evaluate the potential hazards in drinking water. br Shaban and El-Taweel (2002) reported that prechlorination-coagulation step is more or less efficient treatment step in removing the new indicator organisms and photogenic bacterial. In this concept, Payment et al., (1985) concluded that prechlorination removed over 95 % of the density of microorganisms in water. Also, they added that prechlorination-coagulation-sedimentation process appeared to be the most efficient step in reducing number of microorganisms in the raw water. With regards to the results of other treatment steps (sedimentation, filtration and postchlorination), the water was free -#102;-#114;-#111;-#109; classical bacterial indicators but contains all of new indicator organisms and pathogenic bacteria. Thus, these treatment steps in the three systems did not remove but might add microorganisms to the water. Therefore, the presence of the testes parameters in the final treated water declared that; the treatments are not adequate or there is a failure in the treatment systems. br 3.1. Bacterial indicators of water quality br Water contaminated by fecal material -#102;-#114;-#111;-#109; human and animals may contain a large verity of pathogenic microorganisms. Health protection programs require estimating the level of contamination in water by these pathogens. Thus, various bacterial indicators are usually used to evaluate the fecal contamination in water. For years, TC and FC were the most widely used bacterial indicators but, the abundance of E. coli has been shown to be more related to the sanitary risk than other coliforms (Fewtrell and Bartram, 2001). br 3.1.1. Heterotrophic plate count (HPC) br HPC formerly known as the standard plate count (SBC), total viable bacterial count (TVBC) and total bacterial counts (TBC). Colonies may arise -#102;-#114;-#111;-#109; pairs, chains, clusters or single cells, all expressed in colony forming units (CFU) (APHA, 2011). br HPC represents in the aerobic and facultative anaerobic bacteria that derive their carbon and energy -#102;-#114;-#111;-#109; organic compounds. This group includes; pseudomonas, Aeromonas, Klebsiella, Flavobacterium, Enterobacter, Citrobacter, Serratia, Acinetobacter, Proteus, Alcaligences, Moraxella and nontubercular mycobacteria (e.g., Aeromonas, Flavobacterium), and high numbers of HPC effect on Human health (Bitton,2005) br Bacteria recovered through HPC tests generally include natural origin bacteria (non-hazardous) and may be including pathogenic bacteria in polluted water (Bartram et al., 2003). br HPC testing has a long history of use in water microbiology. At the end of the 19th century, HPC tests were employed as indicators of the treatment processes and indirect indicators of water safety. The use of HPC as a safety indicator declined with the adoption of specific fecal indicator bacteria during the 20th century (Bartram et al., 2003). br HPC measurements are used to (a) indicate the effectiveness of water treatment process thus, as an indirect indication of pathogen removal, (b) measure the number of regrowth microorganisms that may or may not have sanitary significance, and (c) measure of possible interference with coliform measurements in lactose based culture methods (Bartram et al., 2003). br HPC level in drinking water must not exceed 500 CFU/ml (Bitton, 2005), and in some countries allow HPC of 100 CFU/ml (SABS, 2001; WHO, 2002). In Egypt the HPC must not exceed 50 CFU/ml (Egyptian Standard, 2007). Numbers above this limit generally signal a deterioration of water quality in distribution systems (Bitton, 2005). br 3.1.2. Total coliform (TC) br TC belongs to the family Enterobacteriaceae and includes the aerobic and facultative anaerobic, Gram-negative, non-spore forming, rod-shaped bacteria that ferment lactose with gas production within 48 h at 370C (Haller et al., 2009; APHA, 2011). Its presence indicates that fecal pollution may have occurred and pathogens might be present. To ensure absence of enteric pathogens, enumeration of appropriate indicator organisms is required (Schraft and Watterworth, 2005).TC includes E. coli, Enterobacter, Klebsiella and Citrobacter (LeChevallier et al., 1983). These coliforms are discharged in relatively high numbers (2.0 x 109coliforms/day/capita) in human and animal feces, but not all of them are of fecal origin. Although many coliform bacteria and other indicator organisms may not be pathogenic, their presence in water may signal the presence of potentially pathogenic agents including viruses -#102;-#114;-#111;-#109; the intestinal tract of warm blood animals (Noble et al., 2003; Haller et al., 2009). TC is used to monitor treated water supplies with the objective to determine adequacy of the water treatment process and integrity of the distribution system (Schraft and Watterworth, 2005). Coliforms and E. coli are of great importance among bacterial indicators used in water quality definition and health risk (Giannoulis et al., (2005). br 3.1.3. Fecal coliforms (FC) br Fecal coliform referred to thermotolerant coliform (Alonso et al., 1999; Toranzos et al., 2002).This group includes those coliform that ferment lactose at 44ºC. Since levels of fecal coliforms are mostly directly correlated to those of E. coli, fecal coliform counts have been widely accepted for routine monitoring of water quality (Toranzos et al., 2002; Kamel, 2006). The use of indicator bacteria such as fecal coliforms (FC) and fecal streptococci (FS) for assessment of fecal pollution and possible water quality deterioration in fresh water sources is widely used (APHA, 2005). Fecal coliform bacteria may enter the aquatic environment directly -#102;-#114;-#111;-#109; human and animal waste inputs, agriculture and storm runoff, and -#102;-#114;-#111;-#109; wastewater. Putheti and Leburu (2009) reported that domestic, industrial wastewater and agriculture waste environment are sources of fecal bacterial to rivers. Fecal coliform concentrations are important for evaluating a water body’s compliance with water quality criteria (Sargeant et al., 2005). br Fresh water polluted by fecal discharges -#102;-#114;-#111;-#109; men and animals may transport a variety of human pathogenic microorganisms (viruses, bacteria and protozoa). Because the detection of all waterborne fecal pathogens is very difficult, various indicators of fecal contamination are usually used to detect fecal pollution in natural waters. The abundance of these indicators is supposed to be correlated to the density of pathogenic microorganisms -#102;-#114;-#111;-#109; fecal origin and thus an indication of the sanitary risk associated with the various water utilizations (Bathing, shellfish harvesting or production of drinking water). For years, the fecal coliforms (FC) have been the most widely used as fecal indicators (US-EPA, 1999 and WHO, 2001). br 3.1.4. Fecal Streptococci (FS) br A group of Gram positive coccid bacteria known as fecal streptococci (FS) were being investigated as important pollution indicator bacteria (Geldreich, 1976). Generally the occurrence of fecal streptococci in water suggests recent fecal pollution.Whereas, their absence indicates with no warm-blooded animal contamination. Taxonomically fecal streptococci belong to the genera Enterococcus and streptococcus. The genus Enterococcus now includes all streptococci that share certain biochemical properties and have a wide tolerance of adverse growth conditions (WHO, 1995). br The enterococcus group is subgroup -#102;-#114;-#111;-#109; FS that includes streptococcus facalis, S. faecium, S. gallinarum, and S. avium. Enterococci are differentiated -#102;-#114;-#111;-#109; other streptococci by their ability to grow in 6.5 % NaCl, at pH 9.6, and at 10ºC and 45ºC. Enterococci portion of FS in a valuable bacterial indicator for determining the extent of fecal contamination of recreational surface water. Studies at marine and fresh water bathing water and beaches included that swimming associated gastroenteritis is related directly to the quality of the bathing water and that enterococci are most efficient bacterial indicator of water quality (APHA, 2011). With respect to the relative proportion of fecal coliforms and fecal streptococci, fecal streptococci species profiles and especially whether those -#99;-#104;-#97;-#114;acteristics can be used to distinguish between human and animal effluent (Sinton and Donnison, 1994). Furthermore, streptococci are highly resistant to drying and may be valuable for routine control after laying new mains or repairs in distribution systems or for detecting pollution by runoff to round or surface water (Meier et al., 1997; WHO, 2001 and 2004). There are four key points in favor of the fecal streptococci were relatively high numbers in the excreta of humans - other worm-blooded animals, present in wastewater - known polluted waters, absence -#102;-#114;-#111;-#109; pure water, virgin soils and environmental having no contact with human and animal life and persistence without multiplication in the environment (Catalna et al., 1996). br Finally, FC and FS are traditionally used as bacterial indicator to ensure microbiological safety of drinking water, natural water resources and wastewater (Sidhu and Toze, 2009). br 3.2. Other pathogenic bacteria in water br 3.2.1. E. coli O157H:7 br E. coli is a genetically diverse species with the majority of its members being nonpathogenic and part of the natural gut microflora of human and animals (Eblen, 2007). E. coli was not identified as human pathogen until the early 1940’s (Bray and Beavan, 1948). E. coli O157:H7 was first recognized as an enteric pathogen in 1982 in the Centre for Disease Control and Prevention (CDC) during the period -#102;-#114;-#111;-#109; 1982 to 1993, at least 20 outbreaks of E. coli O157:H7 have been reported in the USA (USDA, 1994). Some pathogenic E. coli has a low infectious dose. The infectious dose for E. coli O157:H7 is estimated to be small, ranging -#102;-#114;-#111;-#109; 10 to 100 cells (Bell et al., 1994).These outbreaks have affected 1.509 patients, resulting in the hospitalization of 346 patients, 86 cases of hemolytic uremic syndrome (HUS), and 19 deaths. In 1993, 13 outbreaks and in 1994, 30 outbreaks were recorded (Armstrong et al., 1996). It has since been -#99;-#104;-#97;-#114;acterized in several laboratories as causing self-limiting diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura in children and other susceptible groups of individuals (Doyle, 1991; Meng et al., 2001). Outbreaks of E. coli O157:H7 infections have been primarily associated with eating undercooked ground beef, but a variety of other foods have also been implicated as vehicles. Cross-contamination of foods can occur in food-processing plants and during subsequent handling and preparation, resulting in a wide range of foods being implicated in outbreaks of E. coli O157:H7 infections (Mead et al., 1999; IFT, 2001; Beuchat, 2002). br E. coli O157:H7 is known to produce exopolysaccharides (EPS) (Grant et al., 1969; Junkins and Doyle, 1992; Mao et al., 2001), which can provide a physical barrier to protect cells against environmental stresses. EPS is also involved in cell adhesion and biofilm formation (Weiner et al., 1995; Frank, 2000). EPS can serve as a conditioning film on inert surfaces (Allison and Sutherland, 1987) affect cell attachment by functioning as an adhesive or anti-adhesive (Ofek and Doyle, 1994), and influence the formation of three-dimensional biofilm structures (Danese et al., 2000). We have observed that EPS produced by E. coli O157:H7 acts as an anti-adhesive, affecting the attachment of cells on the surface of stainless steel (Ryu et al., 2004). Cells in biofilm produced by an EPS-overproducing mutant had enhanced resistance against environmental stresses imposed by nutrient limitationin lettuce juice compared to that of cells in biofilm formed by a strain not overproducing EPS. Resistance of cells embedded in biofilm to sanitizers was not investigated in that study (Ryu et al., 2004). br E. coli O157:H7 has also been shown to produce curli, a thin, coiled fimbriae-like extracellular structure. Unlike nonpathogenic E. coli, curli production by E. coli O157:H7 is uncommon but can occur in association with csgD promoter point mutations (Uhlich et al., 2001). Curli produced by nonpathogenic E. coli enhanced the attachment of cells on the surface of polystyrene (Vidal et al., 1998; Prigent-Combaret et al., 2000). br 3.2.2. Pseudomonas aeruginosa br Pseudomonas aeruginosa is an opportunistic pathogen, which can be isolated -#102;-#114;-#111;-#109; different aquatic habitats, including biofilms in natural fresh water environments and in technical water systems (Costerton et al., 1990; Botzenhart and Döring, 1993; Grobe et al., 1995). The emergence of P. aeruginosa in chlorinated swimming-pools and whirlpools has been reported (Botzenhart et al., 1974; Schindler et al., 1978; Seyfried and Fraser, 1980; Carmienke and Partisch, 1991) and associated with increased risk of certain infections such as dermatitis, folliculitis, otitis externa or conjunctivitis (Thomas et al., 1985; Ratnam et al., 1986; Hunter, 1996). The production of slime may be a potential mechanism of bacterial resistance against chlorine (Seyfried and Fraser, 1980). Slime-forming (mucoid) variants of P. aeruginosa are -#99;-#104;-#97;-#114;acterized by an over production of the viscous extracellular polysaccharide alginate.Which represents amajor structural component in biofilms formed by these bacteria (Davies, 1999). The survival of a mucoid P. aeruginosa strain in chlorinated water was compared to that of an isogenic nonmucoid strain in an attempt to evaluate the influence of alginate slime formation on bacterial survival in chlorinated water systems Pseudomonas aeruginosa. br 3.2.3. Bacillus subtilis br B. subtilis can be isolated -#102;-#114;-#111;-#109; many environments – terrestrial and aquatic-making it seem that this species is ubiquitous and broadly adapted to grow in diverse settings within the biosphere. However, like all members of the genus Bacillus, B. subtilis can form highly resistant dormant endospores in response to nutrient deprivation and other environmental stresses (Sonenshein et al., 2002 and Ricca et al., 2004). These spores are easily made airborne and dispersed by wind (Jaenicke, 2005; Merrill et al., 2006). Thus, spores might migrate long distances, land in a given environment but never germinate there. Considering that the traditional methods for isolating B. subtilis require that the organism be in its spore form, there is no guarantee that when a strain is isolated -#102;-#114;-#111;-#109; a particular environment it was actually growing at that location. Thus, the question of -#119;-#104;-#101;-#114;-#101; B. subtilis grows has not been so simple to answer (Felske, 2004; Nicholson, 2004). B. subtilis is often referred to as a ‘soil dweller’. Does B. subtilis actually grow in soil or is this a place -#119;-#104;-#101;-#114;-#101; spores accumulate until they encounter conditions suitable for their germination and proliferation? Over 30 years ago, the use of fluorescent antibodies to distinguish vegetative and spore forms of B. subtilis in diverse soil samples (Norris and Wolf, 1961) revealed that the organism was most often inits vegetative form when associated with decaying organic material (Siala et al., 1974). Although this early study is the only one to date that has directly examined growth in natural soils, further support for the idea that B. Subtilis can lead a saprophytic lifestyle comes -#102;-#114;-#111;-#109; recent experiments in which spores were inoculated into artificial soil microcosms saturated with filter-sterilized soluble organic matter extracted -#102;-#114;-#111;-#109; soil (Vilain et al., 2006). Under these conditions the spores not only germinated but the vegetative cells proliferated for several days until they again speculated, probably in response to nutrient depletion. Soon after germination the cells formed bundled chains that moved on the surface in a flagella-independent fashion (Vilain et al., 2006). Interestingly, a similar transition to growth as bundled chains is observed during the early stages of biofilm development under laboratory conditions (Branda et al., 2001). B. subtilis can also grow in close association with plant root surfaces. In the laboratory, when B. subtilis was inoculated on the roots of Arabidopsis thaliana, growth of biofilms was observed (Bais et al., 2004; Rudrappa et al., 2007). In addition, B. subtilis can be isolated in greater numbers than most other spore forming bacteria -#102;-#114;-#111;-#109; the rhizosphere of a variety of plants (Fall et al., 2004; Cazorla et al., 2007). There is evidence that through these associations’ B. subtilis can promote plant growth (Cazorla et al., 2007). Possible explanations for this growth promotion are that: (i) B. subtilis outcompetes other microbes that would otherwise adversely affect the plant; (ii) B. subtilis activates the host defense system so that the plant is poised to resist potential pathogens; or (iii) B. subtilis makes certain nutrients more readily available to the plant (e.g. phosphorus and nitrogen) (Nagorska et al., 2007). Considering that B. subtilis is found on and around plants and that many animals consume plants, it is not surprising that this bacterium is often found in feces (Nicholson, 2004; Barbosa et al., 2005; Leser et al., 2008). Passage of B. subtilis through animal gastrointestinal (GI) tracts might not be without effects; the idea that B. subtilis has an active role within the GI tract has had anecdotal support for years. In fact, B. subtilis has been touted as a probiotic that when ingested has ‘beneficial ‘effects, probably by helping to maintain or restore ‘healthy’ bacterial communities in the body (Hong et al., 2005). B. subtilis is also found in several commercially available fermented food products, including soybeans fermented with B. subtilis natto, which is popular in Japan and has long been thought to confer health benefits (Inatsu et al., 2006). But like its role in plant growth promotion, it is not fully understood how B. subtilis imparts its probiotic effect.Staphylococcus epidermidis.