الفهرس 
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Abstract
Plants provide complex micro-ecosystems where different habitats can be
harbored by a wide variety of microbes. Endophytic bacteria can be defined as
those bacteria that colonize the internal tissue of the plant showing no external
sign of infection or negative effect on their host.
Endophytic microbes have been known as possible useful sources of
bioactive secondary metabolites that may be involved in a host-endophyte
relationship. Recently, many endophytic bioactive metabolites, known as well as
new substances, possessing a wide variety of biological activities as antibiotic,
antitumor, anti-inflammatory, antioxidant have been identified. Endophytic
bacteria may be very interesting for biotechnological production of bioactive
substances as medicinally therapeutic important agents.
Plants growing in unique environmental settings with ethnobotanical value
and longevity or endemic location are likely to be a source of rarely occurring
novel microbial endophytes. Endophytes isolated from Capparis sinaica in
Hammam Faraoun, Sinai, Egypt, were selected for this study because that area
shows unique environmental settings of novel microbial endophytes and there is
scarce information on the characterization of its endophytes. C. sinaica is a
promising medicinal herb mentioned in ancient ayurvedic literature as having
great economic potential. The plant is indigenous to the Sinai and is used in
traditional medicines to cure various illnesses.
The endophytic bacteria of medicinal plants could produce medicinally
important metabolites originally produced by their hosts and hence, obtaining
bioactive compounds from microbial production via fermentation instead of
from a natural source would not only reduce the need to harvest slow growing
and possibly rare plants but also preserve the world’s ever diminishing
biodiversity. Furthermore, it is recognized that a microbial source of a valued
product may be easier and more economical to produce, effectively reducing its
market price.The reason why some endophytes produce certain phytochemicals
originally characteristic of the host might be related to a genetic recombination
of the endophyte with their host that occurs in evolutionary time.
The present work focused on isolation, characterization and identification of
cultivable endophytic bacteria that colonize aerial parts of C. sinaica, which
were used in the treatment of several human diseases, as a medicinal plant in
North Sinai-Egypt, with intention to study some bioactive compounds produced
by plant (aerial parts).The mixed microbial culture system of isolated
endophytic bacterial strains were screened for production of the same bioactive
compounds detected in plant extract. So this type of comprehensive study might
shed the light on the possible symbiotic relationship between plant and
endophytic bacteria living inside it and possible role of endophytic bacteria in
the synthesis of the medicinally important compounds originally produced by C.
sinaica.
Endophytic bacteria were isolated from fresh healthy surface sterilized
segments of aerial parts of C. sinaica under aseptic conditions following two
methods; The first method include the isolation from surface-sterilized
segmentsplaced on nutrient agar plates, where in the second method, dilution of
the suspension resulted from the maceration of plant segments was used to
inoculate nutrient agar plates (plating a suspension of macerated homogenized
segments in saline). The morphological, biochemical and 16Sr RNA gene
sequence analysis of selected endophytic bacterial isolates led to the
identification of 10 different bacterial strains belonging to different strains of
genus Bacillus (B. subtilis, B. amyloliquefaciens subsp. Plantarum and Bacillus
benzoevorans).
To confirm the successful isolation of true endophytic bacteria over this
study the sterility check of plant segments was conducted which proved the
absolute absence of any growth of bacteria in the final rinsing solution, and
visualizing endophytic bacteria in its natural niche inside plant tissue. Stained
transverse sections (T.S.) of plant roots with tetrazolium dye revealed the
presence of pink color stained bacteria typical appearance of endophytic bacteria
in intercellular spaces of cortex and pith area as well as around xylem vessels.
Bioactive metabolites produced by C. sinaica and endophytic bacteria were
identified using three successive tests namely, preliminary phytochemical
screening, paper chromatography and HPLC analysis. Preliminary
phytochemical screening of both extracts of C. sinaica and endophytic bacterial
extra cellular culture extracts of nutrient broth supplemented with 3% glucose
(F2) and of enrichment medium (F3) showed positive results for flavonoids,
Saponins, terpenoids and glycosides in different concentrations and indicate that
flavonoids represented a major constituent of both plant and endophytic
bacterial extracts (F2) and (F3). Paper chromatography and HPLC analysis were
conducted for tracking of flavonoids found in both extracts of plant and bacterial
extra cellular culture filtrate.
The result showed that plant extract produces several flavonoid compounds
(quercetin, quercetin 3-O-glucopyranoside, quercetin 3-rutinoside, isorhamnetin
3-rutinoside and kaempferol 3-rutinoside), while bacterial extracts produce only
quercetin and quercetin 3-O-glucopyranoside. Hence, it was concluded that
endophytic bacteria produced flavonoid compounds similar to that originally
produced by the plant itself that confirming the possible symbiotic relationship
between plant and endophytes.
Endophytic bacteria living inside the plant, supporting the idea that these
bacteria may induce the plant to synthesize specific compounds and they could
improve the plant content of these bioactive compounds. The associated
endophytic bacteria confirm production of bioactive flavonoid such as quercetin
which has antioxidant and anti-inflammatory activity.
Endophytic bacteria possess the ability to produce and/or synthesized some
bioactive compounds in vitro which provide the idea of considering endophytes
as the potential sources of novel natural products for exploitation in pharmacy,
medicine, agriculture and industry.