marine environment (Hara et al. 2004). About 2Á37 million tons of oil are introduced into the seas every year
(GESAMP 1993). Petroleum hydrocarbons come to the
environment from a variety of sources, both natural and
anthropogenic: terrestrial and freshwater run-off, crude
oil spills, refuse from coastal oil refineries, offshore oil
production, shipping activities, and accidental spillage of
fuels and other petroleum products all contribute to marine pollution (Yakimov et al. 1998). Crude oil can be
classified into four main operationally defined groups of
chemicals: the saturated hydrocarbons and the aromatic
hydrocarbons, and the more polar, non-hydrocarbon
components the resins and the asphaltenes. Many of these
constituents are difficult to degrade and highly toxic due
to presence of hemotoxic, carcinogenic and teratogenic
components and cause severe environmental damages
that may directly or indirectly affect human health and
ecological systems (Chandra et al. 2013). Several
approaches including physical, chemical and biological
strategies have been developed and used to remove
hydrocarbons from polluted sites. Mechanical and chemical methods have been shown to be expensive and alter
the natural ecosystem by generating more toxic products
and an incomplete removal of these pollutants. For this
reason, an increasing attention has been directed towards
the research of new strategies and environmental-friendly
technologies to be applied for the remediation of contaminated sites by hydrocarbons. Bioremediation technology uses micro-organisms to degrade toxic pollutants to
harmless products such as CO 2 and H 2 O, and other inorganic compounds and these processes are environmentally safe and cost-efficient (Fathepure 2014). In general,
bioremediation is based on in situ stimulation of the
microbial communities (biostimulation) or amending the
microbial community with an inoculum of hydrocarbondegrading bacteria (bioaugmentation) (Catania et al.
2015).
Biodegradation by natural populations of micro-organisms is the most reliable mechanism by which thousands
of xenobiotic pollutants, including crude oil, are eliminated from the environment (Cappello et al. 2007).
Diverse petroleum-degrading bacteria such as Alcanivorax
(Yakimov et al. 1998), Cycloclasticus (Dyksterhouse et al.
1995), Marinobacter (Gauthier et al. 1992), Neptunomonas
(Hedlund et al. 1999), Oleiphilus (Golyshin et al. 2002)
and Oleispira (Yakimov et al. 2003) have been isolated
from marine environments and have been shown to play
a key role in the removal of hydrocarbons from polluted
environments (Yakimov et al. 2007). Pollution by petroleum hydrocarbons stimulates the growth of such organisms and causes changes in the structure of microbial
communities in the contaminated area (Harayama
et al. 2004). The proportions of hydrocarbon-degrading
bacterial populations in hydrocarbon-contaminated marine environments often exceed 10% of the total bacterial
population (Atlas 1981). These bacteria have the property
of emulsifying hydrocarbons in solution by producing
surface-active agents such as biosurfactants that increase
the adhesion of cells to the substrate and reduce interfacial tension between the aqueous and the organic phases
which leads to increased bioavailability and subsequent
biodegradation of the hydrocarbons (Batista et al. 2006).
Microbial degradation of crude oil often occurs first by
the attack of alkanes, which are major components of
crude oil. Alkane hydroxylase is a key enzyme involved in
alkane degradation in Gram-negative and Gram-positive
bacteria (Quatrini et al. 2008). This enzyme introduces
an oxygen atom derived from molecular oxygen into the
alkane substrate and plays an important role in crude oil
bioremediation (Van Beilen et al. 2003).
There have been many studies about the microbial
communities participating in the degradation of pollutants in the Mediterranean Sea especially in the northern
side of the basin. The southern side remains poorly studied, despite many of the southern countries being major
oil producers and exporters (Daffonchio et al. 2013). As
one of the top three oil producers in Africa and with a
coastline of 1622 km along the Mediterranean south
shore, Algeria is a major stakeholder in the oil pollution
in the Western Basin of the Mediterranean Sea. In 2015,
the country produced about 1Á7 million barrels per day
of total petroleum products. More than 75% of this production was exported by sea. In terms of gross input of
organic matter, hydrocarbons pollution has been mentioned as one of the primary environmental problems
along the Algerian coast (Benmecheta and Belkhir 2016).
The present work aims to provide knowledge about
indigenous bacterial strains involved in the bioremediation of hydrocarbons. It is indeed the native microflora
that determines the self-purification capacities of the site
in the absence of any physico-chemical limitation. The
aim was to isolate and characterize hydrocarbon-degrading bacteria from an oil-polluted harbour in the central
part of Algeria (Sidi Fredj). The main characteristics
investigated were: (i) the ability to grow in the presence
of different hydrocarbons, (ii) the biosurfactants production, (iii) the oil fractions degradation and (iv) the presence of catabolic genes involved in aliphatic and aromatic
hydrocarbons degradation
Materials and methods
Study area and samples collection
Sidi Fredj is a marina built in 1970 located along the west
coast of Algiers (Centre Algeria, south Mediterranean sea,
Journal of Applied Microbiology 126, 780--795 © 2018 The Society for Applied Microbiology
781
N. Djahnit et al.
The use of oil-degrading bacteria as an alternative for environmental remediation (bioremediation)
(GESAMP 1993). Petroleum hydrocarbons come to the
environment from a variety of sources, both natural and
anthropogenic: terrestrial and freshwater run-off, crude
oil spills, refuse from coastal oil refineries, offshore oil
production, shipping activities, and accidental spillage of
fuels and other petroleum products all contribute to marine pollution (Yakimov et al. 1998). Crude oil can be
classified into four main operationally defined groups of
chemicals: the saturated hydrocarbons and the aromatic
hydrocarbons, and the more polar, non-hydrocarbon
components the resins and the asphaltenes. Many of these
constituents are difficult to degrade and highly toxic due
to presence of hemotoxic, carcinogenic and teratogenic
components and cause severe environmental damages
that may directly or indirectly affect human health and
ecological systems (Chandra et al. 2013). Several
approaches including physical, chemical and biological
strategies have been developed and used to remove
hydrocarbons from polluted sites. Mechanical and chemical methods have been shown to be expensive and alter
the natural ecosystem by generating more toxic products
and an incomplete removal of these pollutants. For this
reason, an increasing attention has been directed towards
the research of new strategies and environmental-friendly
technologies to be applied for the remediation of contaminated sites by hydrocarbons. Bioremediation technology uses micro-organisms to degrade toxic pollutants to
harmless products such as CO 2 and H 2 O, and other inorganic compounds and these processes are environmentally safe and cost-efficient (Fathepure 2014). In general,
bioremediation is based on in situ stimulation of the
microbial communities (biostimulation) or amending the
microbial community with an inoculum of hydrocarbondegrading bacteria (bioaugmentation) (Catania et al.
2015).
Biodegradation by natural populations of micro-organisms is the most reliable mechanism by which thousands
of xenobiotic pollutants, including crude oil, are eliminated from the environment (Cappello et al. 2007).
Diverse petroleum-degrading bacteria such as Alcanivorax
(Yakimov et al. 1998), Cycloclasticus (Dyksterhouse et al.
1995), Marinobacter (Gauthier et al. 1992), Neptunomonas
(Hedlund et al. 1999), Oleiphilus (Golyshin et al. 2002)
and Oleispira (Yakimov et al. 2003) have been isolated
from marine environments and have been shown to play
a key role in the removal of hydrocarbons from polluted
environments (Yakimov et al. 2007). Pollution by petroleum hydrocarbons stimulates the growth of such organisms and causes changes in the structure of microbial
communities in the contaminated area (Harayama
et al. 2004). The proportions of hydrocarbon-degrading
bacterial populations in hydrocarbon-contaminated marine environments often exceed 10% of the total bacterial
population (Atlas 1981). These bacteria have the property
of emulsifying hydrocarbons in solution by producing
surface-active agents such as biosurfactants that increase
the adhesion of cells to the substrate and reduce interfacial tension between the aqueous and the organic phases
which leads to increased bioavailability and subsequent
biodegradation of the hydrocarbons (Batista et al. 2006).
Microbial degradation of crude oil often occurs first by
the attack of alkanes, which are major components of
crude oil. Alkane hydroxylase is a key enzyme involved in
alkane degradation in Gram-negative and Gram-positive
bacteria (Quatrini et al. 2008). This enzyme introduces
an oxygen atom derived from molecular oxygen into the
alkane substrate and plays an important role in crude oil
bioremediation (Van Beilen et al. 2003).
There have been many studies about the microbial
communities participating in the degradation of pollutants in the Mediterranean Sea especially in the northern
side of the basin. The southern side remains poorly studied, despite many of the southern countries being major
oil producers and exporters (Daffonchio et al. 2013). As
one of the top three oil producers in Africa and with a
coastline of 1622 km along the Mediterranean south
shore, Algeria is a major stakeholder in the oil pollution
in the Western Basin of the Mediterranean Sea. In 2015,
the country produced about 1Á7 million barrels per day
of total petroleum products. More than 75% of this production was exported by sea. In terms of gross input of
organic matter, hydrocarbons pollution has been mentioned as one of the primary environmental problems
along the Algerian coast (Benmecheta and Belkhir 2016).
The present work aims to provide knowledge about
indigenous bacterial strains involved in the bioremediation of hydrocarbons. It is indeed the native microflora
that determines the self-purification capacities of the site
in the absence of any physico-chemical limitation. The
aim was to isolate and characterize hydrocarbon-degrading bacteria from an oil-polluted harbour in the central
part of Algeria (Sidi Fredj). The main characteristics
investigated were: (i) the ability to grow in the presence
of different hydrocarbons, (ii) the biosurfactants production, (iii) the oil fractions degradation and (iv) the presence of catabolic genes involved in aliphatic and aromatic
hydrocarbons degradation
Materials and methods
Study area and samples collection
Sidi Fredj is a marina built in 1970 located along the west
coast of Algiers (Centre Algeria, south Mediterranean sea,
Journal of Applied Microbiology 126, 780--795 © 2018 The Society for Applied Microbiology
781
N. Djahnit et al.
The use of oil-degrading bacteria as an alternative for environmental remediation (bioremediation)