الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
Antimicrobial resistance has become one of the most pressing issues in
modern medicine, as well as a major threat to public health, due to the
emergence, spread, and persistence of multidrug-resistant (MDR) bacteria
(Deslouches, et al 2017, Kamenshchikova et al 2021). To avoid the lethal
threat posed by antibiotic-resistant microbes, immediate and coordinated action
is required, such as the development of new antimicrobial agents with high
efficacy against resistant pathogenic microorganisms.
Antimicrobials are drugs used to impede, alleviate, or treat illnesses
caused by pathogens. These drugs can be grouped into various classes according
to the attacked pathogens, such as antibiotics, antivirals, antifungals, and
antiparasitics. Antibiotics cure bacterial illnesses by attacking bacteria either by
killing them or reducing their development and proliferation (Eric et al. 2016).
Depending on their method of attack, antibiotics can interfere with cell wall
formation, protein buildup, and nucleic acid generation, disrupting membrane
functions and metabolic processes in pathogens (Hale and Hancock 2007).
Based on their molecular structures, antibiotics are grouped as
quinolones, macrolides, sulphonamides, β-lactams, tetracyclines,
aminoglycosides, glycopeptides, and oxazolidinones (Etebu and Arikekpar
2016). Antibiotics are classified as narrow, wide, or extended-spectrum
medicines based on their mode of action. Penicillin G and other antibiotics with
a restricted range of action are particularly effective against gram-positive
bacteria. Tetracycline and chloramphenicol with a wide range of action that
target both gram-positive and gram-negative bacteria (Shin et al. 2015).
Bacterial infection has been linked to cancer through two mechanisms:
the first is the development of chronic inflammation, such as that caused by
Helicobacter pylori in the stomach, which is one of the leading causes of
stomach cancer. The second phase involves the production of mutagenic and
carcinogenic bacterial metabolites. This concept is best illustrated by colon
cancer (Vogelmann and Amieva 2007). Although in vivo research on the
carcinogenesis of bacterial metabolites is conflicting, developing a medication
that not only has antibacterial activity but also has potent anti-inflammatory and
antioxidant properties is warranted. This strategy will inhibit negative outcomes
associated with bacterial infections and provide protective biological tools.
Even with recent great medical improvements, human cancer is a major
cause of mortality globally (Deslouches and Di 2017). Chemotherapeutics are
the main treatment for advanced cancer, but they impose substantial health risks
and encourage multi-drug resistant traits establishment. Instead, massive
initiatives have been undertaken recently to create novel natural therapeutics
that are effective but less damaging to patients, such as extracts of plant lichen
(Thombre et al. 2016; El-Garawani et al. 2020; El-Garawani et al. 2021),
and insects Microbial peptides (MPs) have anticancer effects, according to
emerging data (Deslouches et al. 2015), and are an underutilized resource with
a low likelihood to acquire resistance or cause harm to healthy cells (Siegal et
al. 2014). MPs may electrostatically adhere to the negatively charged outer
membranes of cancer cells, and so produce cytotoxic effect on malignant cells
via necrosis or apoptosis (Figueiredo et al. 2014; Ting et al. 2014; Deslouches
and Di 2017; Tornesello et al. 2020). Consequently, MPs have already shown
promise as bioactive agents that either kill or limit malignant cells proliferation.
Among bacterial species known for their ability to produce antimicrobial
and antitumor agents, Brevibacillus sp. has recently been described as a
promising candidate for producing multiple short-sequence MPs along with
antimicrobial agents such as glycopeptides, brevibacillin, and bacteriocin
(Krachkovskii et al. 2002). It was described as a facultative anaerobic, grampositive, and endospore-forming bacterium (Laubach 1916), then Brevibacillus
was reclassified from Bacillus (Shida et al. 1996). Brevibacillus can be found in
various environments, including oceans, rivers, sediment, hot springs, soil, and
compost (Singh et al. 2012).
Microorganisms from severe environments have recently received much
attention (Vasavada et al. 2006). Halophilic microorganisms are highly salttolerant microbes. Recent research indicates that halophilic or halotolerant
bacteria from high saline environments produce a wide variety of
biosurfactants, enzymes, and antimicrobial agents (Chamekh et al. 2019; Fariq
et al. 2019; Mainka et al. 2021). Hypersaline environments offer numerous
opportunities for synthesizing secondary metabolites with industrially relevant
bioactivities (Manikandan and Senthilkumar 2017). Several saline
environments are known in Egypt, including the lakes of Wadi Al-Natrun
(Mesbah et al. 2007), the Solar Lake on the Sinai coast of the Gulf of Aqaba
(Cohen et al. 1977), and Mariout lake in Alexandria city (Asker and Ohta
2002), which is one of the Egypt’s biggest lagoons that is subject to
uncontrolled pollution. Mariout Lake is one of the most anthropogenically
degraded and eutrophic wetland in the Nile Delta due to outflows from the
industrial and urban sectors (Eltarahony et al. 2021). The isolated BF202 strain
in this study differs from other reported strains such as JX-5 (GenBank:
KF444391.1) and S62-9 (Genbank: EU709016.1) (Jiang et al. 2017; Chen et al.
2022), where, the 16S rRNA identities of BF202 strain were 99.22% and
99.39%, respectively. Measuring 16S identity revealed that the Brevibacillus
halotolerans was more closely related to BF202 than JX-5 and S62-9 strains.
These findings point to distinctions in the BF202 strain that could be ascribed to
the effect of environmental factors on the genetic structure.
More attention is needed to explore the halophilic dwelling bacteria of the
Egyptian hypersaline habitats and thus scrutinize their bioactivities (ElGarawani, et al. 2020). This research aims to isolate halophilic and halotolerant
bacteria from a hypersaline lake in Egypt and studying their antimicrobial
activities. Initially, this research focused on identifying and characterizing the
marine B. laterosporus BF202, isolated from the silt of Mariout lake in
Alexandria, Egypt. Identifying the B. laterosporus BF202 bioactive metabolites
will lead to the developing of new antibacterial agents. To the best of our
knowledge, using LC-MS-MS analysis, identifying certain diketopiperazines,
investigating antibacterial potentials in the crude extract of marine B.
laterosporus isolated from Egypt is a novel aspect of this study. The species
was investigated as a part of our ongoing project on chemical and biological
studies of natural organisms