11.2 Characteristics of Marine Microorganisms
Marine microorganism habitats possess a number of characteristics that distinguish
them from land environments, including high salinity, high pressure, low temperature, and low nutrients. To adapt to these complex living environments, marine
microorganisms have adopted halophilic, psychrophilic, barophilic, photic, and
polymorphic characteristics (Arrigo 2004).
1. Halophilic: This is the most general characteristic of marine microorganisms:
they require seawater as a basic environment to achieve optimal growth. These
organisms typically exhibit optimal growth at a 30% saline concentration. Also
obtainable from seaweed are trace elements and organic salts necessary for
marine microorganism growth and metabolism, including potassium, magnesium, and calcium (Kokare et al. 2004).
2. Psychrophilic: Over 90% of ocean volume consists of environments with
temperatures of 5 °C or less. Marine microorganisms must therefore be capable
of growth at low temperatures. Marine microorganisms typically cannot grow at
temperatures above 37 °C (D’Amico et al. 2006).
3. Barophilic: This refers to marine microorganisms’ ability to inhabit
high-pressure environments. It is typically found in the organisms that inhabit
the bottom of ocean, where pressures exceed 380 atm. Some bacteria in the
Pacific Ocean have been found inhabiting sea bottom areas with maximum
pressures of around 1155 atm. Because of this resistance to high pressures,
barophilic bacteria have been able to adapt to deep-sea environments (Horikoshi
1998).
4. Low-nutrient: Seawater does not contain many nutrients, which means that
some marine bacteria must be cultured in low-nutrient media. When cultured in
nutrient-rich media, marine bacteria die off quickly as they form their initial
colony.
5. Photic: Bioluminescent bacteria represent one of the more interesting groups of
bacteria inhabiting the seas, thanks to their ability to convert chemical energy to
light energy and produce green or blue light. Attempts are currently being made
to take advantage of this bioluminescence phenomenon by using photobacterium as indicators for investigating seawater pollution (Baharum et al. 2010).
6. Polymorphic: Having adapted to grow in complex marine environments, marine
microorganisms exist in various forms. This phenomenon is observable under a
microscope. In particular, polymorphism can be universally observed in
Gram-negative coccus bacteria.
11.2.1 Psychrophilic Microorganisms
Marine environments are inhabited by many microorganisms that reflect the characteristics of those environments. Apart from the surface layers in tropical and
11.2 Characteristics of Marine Microorganisms
383
Marine microorganism habitats possess a number of characteristics that distinguish
them from land environments, including high salinity, high pressure, low temperature, and low nutrients. To adapt to these complex living environments, marine
microorganisms have adopted halophilic, psychrophilic, barophilic, photic, and
polymorphic characteristics (Arrigo 2004).
1. Halophilic: This is the most general characteristic of marine microorganisms:
they require seawater as a basic environment to achieve optimal growth. These
organisms typically exhibit optimal growth at a 30% saline concentration. Also
obtainable from seaweed are trace elements and organic salts necessary for
marine microorganism growth and metabolism, including potassium, magnesium, and calcium (Kokare et al. 2004).
2. Psychrophilic: Over 90% of ocean volume consists of environments with
temperatures of 5 °C or less. Marine microorganisms must therefore be capable
of growth at low temperatures. Marine microorganisms typically cannot grow at
temperatures above 37 °C (D’Amico et al. 2006).
3. Barophilic: This refers to marine microorganisms’ ability to inhabit
high-pressure environments. It is typically found in the organisms that inhabit
the bottom of ocean, where pressures exceed 380 atm. Some bacteria in the
Pacific Ocean have been found inhabiting sea bottom areas with maximum
pressures of around 1155 atm. Because of this resistance to high pressures,
barophilic bacteria have been able to adapt to deep-sea environments (Horikoshi
1998).
4. Low-nutrient: Seawater does not contain many nutrients, which means that
some marine bacteria must be cultured in low-nutrient media. When cultured in
nutrient-rich media, marine bacteria die off quickly as they form their initial
colony.
5. Photic: Bioluminescent bacteria represent one of the more interesting groups of
bacteria inhabiting the seas, thanks to their ability to convert chemical energy to
light energy and produce green or blue light. Attempts are currently being made
to take advantage of this bioluminescence phenomenon by using photobacterium as indicators for investigating seawater pollution (Baharum et al. 2010).
6. Polymorphic: Having adapted to grow in complex marine environments, marine
microorganisms exist in various forms. This phenomenon is observable under a
microscope. In particular, polymorphism can be universally observed in
Gram-negative coccus bacteria.
11.2.1 Psychrophilic Microorganisms
Marine environments are inhabited by many microorganisms that reflect the characteristics of those environments. Apart from the surface layers in tropical and
11.2 Characteristics of Marine Microorganisms
383