Classification, Morfology, Habitat & Life Cicle of Actinomycetes

Actinomycetes are a group of Actinobacteria found in soil. These bacteria cause the “smell of rain” or petrichor when hit by rainwater. This process occurs because _Actinomycetes_ produce a metabolite called the aromatic compound geosmin, which is hydrolyzed by rainwater and then evaporates.

The classification of Actinomycetes according to Lechevalier et al. (1971) is as follows:  

Kingdom: Bacteria  

Phylum: Actinobacteria  

Class: Actinobacteria  

Order: Actinomycetales  

Family: Actinomycetaceae  

Genus: Actinomyces 

Species: Actinomyces sp.

Morphologically, Actinomycetes bacteria are generally rod-shaped and Gram-positive with high guanine and cytosine content. Actinomycetes are bacteria that have fungus-like characteristics because they have thin filaments like mold. The growth pattern of Actinomycetes and fungi tends to be similar, but fungi are eukaryotes while Actinomycetes are prokaryotic bacteria. Actinomycetes are divided into two groups, namely Streptomycetes and Rare-Actinomycetes, whose growth tends to be slower. In addition, their cell walls contain N-acetylmuramic acid. These bacteria do not have mitochondria but contain 70S ribosomes and a nuclear envelope ranging from 5-20 micrometers.

The body structure of actinomycetes consists of fine threads called hyphae or mycelia. When on a solid surface, mycelium or mycelia can differentiate to form aerial hyphae with the aim of producing reproductive spores. Substrate mycelium produces spores by germinating and forming monopodial structures. The initial stage of spore formation is known as the budding process. Spores can form on the substrate, while aerial mycelium consists of single cells. These bacteria are facultative anaerobes that can grow with or without O₂. This type of bacteria is able to ferment carbohydrates. Actinomycetes colonies can be easily distinguished because they are not slimy or mucoid.

Actinomycetes are bacteria that can live in various places such as soil and the sea.  

1. Soil: Actinomycetes generally live in soil at a pH range for growth of 5-9 with an optimum pH around 7. The distribution of Actinomycetes is highly determined by environmental factors such as pH. The role of actinomycetes in soil is the degradation of complex polymers in the plant decomposition process. The role of this type of Actinobacteria in the rhizosphere is to suppress pathogen growth and synthesize gibberellin and indole acetic acid. Waterlogged soil is not suitable for the growth of these bacteria due to the presence of spores. Streptomycetes generally make up about 70% of microorganisms in soil.  

2. Sea: Marine Actinomycetes can decompose cellulose, chitin, alginate, hydrocarbons, oil, etc. These organisms play an important role in degrading oil in aquatic environments. The suitable temperature for Actinomycetes growth ranges from 25-30°C.

The life cycle of Actinomycetes bacteria starts from various phases. According to Demain and Fang (1995) it is as follows:  

1. Germination: The germination phase is the phase where spores obtain a suitable environment or substrate for growth.  

2. Vegetative growth: This phase is the growth phase of hyphae or mycelium from primary mycelium to secondary mycelium.  

3. Coiling: The phase where bacterial mycelium coils.  

4. Septation: The phase where septa form between vegetative hyphae.  

5. Spore maturation: Mature septa will form spore chains, so that the spores become fragmented.  

6. Spore release: Spores detach and are free in the environment.

Morfology, Classification & Habitat of Rhizopora mucronata

Rhizophora mucronata is a type of mangrove that can grow up to 27 m tall. This mangrove generally has a trunk diameter of 70 cm, a dark trunk color tending toward black with horizontal fissures. R. mucronata is classified as a mangrove that has stilt roots, where aerial roots grow from the lower branches. Mangrove roots have adaptive forms to survive by producing roots that emerge from the soil for air intake. The trunk color of R. mucronata is dark, tending toward blackish. The trunk height can reach 27 m, standing upright, not twining and not grooved. This mangrove trunk grows in the outermost zone with the help of its stilt roots to withstand sea waves.

The leaves of this mangrove are broadly elliptic to elongate toward the seed base, with leaf vein tips tapering, measuring 11-23 x 6-13 cm. This mangrove leaf arrangement is single and opposite. The petiole is on the lower side of the midrib with the seed lobe tip resembling a green stalk with a length of 3-4.5 cm. The leaves are bright green and thick, 16 cm long for the oval shape and 9 cm wide. The upper leaf surface is green while the lower surface is green with black spots. The base of this mangrove is tapering, while the leaf tip is also tapering, with pinnate venation and no gap between the petiole and leaf bud.

Rhizophora mucronata has bisexual flowers, each located on algae. The flowers grow in the leaf axils with a length of 2.5-5 cm and calyx tube length of 1.5 cm. The petal leaves have long-hairy edges, some of which attach to the stamens, while the anther heads are quite numerous. The flower color of R. mucronata mangrove is yellow surrounded by sepals colored yellowish-brown to even reddish. Pollination of this mangrove flower is assisted by insects and wind, which generally occurs from April to October. The fruit resulting from pollination or the hypocotyl is green with a length of about 36-70 cm and has a diameter of 2 cm. The fruit bud is half submerged with a free tip, with a short white stalk. The seed lobes unite to form a body or fleshy part with a stalk-shaped tip up to 2 cm. The fruit remains attached even when half-fallen, with a hypocotyl length range of 40-60 cm. This mangrove fruit has a single seed and the cotyledon neck is yellow when ripe.

The classification of mangrove Rhizophora mucronata is:

Kingdom: Plantae  

Division: Magnoliophyta  

Class: Magnoliopsida  

Order: Myrtales  

Family: Rhizophoraceae  

Genus: Rhizophora  

Species: Rhizophora mucronata

Note: "Divisi" = Division, "Kelas" = Class, "Ordo" = Order, "Famili" = Family. I also corrected the spelling to Rhizophora and Rhizophoraceae to match the scientific standard.

Rhizophora mucronata is one type of mangrove belonging to the Rhizophoraceae family. It is generally found in intertidal sea areas that have hard and sandy substrate characteristics. This mangrove species can grow optimally in substrate areas inundated during normal high tide. R. mucronata is not suitable for hard and sandy substrates, but prefers waters that receive a strong and continuous influence of freshwater. The dominance level of this mangrove can reach 90% of the vegetation growing in a location.

Factors affecting mangrove growth include tides, waves, physiography, topography, climate, dissolved oxygen, salinity, soil and nutrients. Mangroves react differently to variations in the physical environment, so vegetation zones and zones in each area have different patterns as well, depending on physiographic conditions and tidal dynamics, and soil elements. Mangroves that grow farther toward the ocean have higher inundation conditions and higher salinity as well, which certainly affects their distribution. The Rhizophora zone is located behind the Avicennia zone (close to the sea), with soft muddy sediment characteristics.

Mangrove ecosystems

Mangrove comes from a combination of the Portuguese word mangue and the English word grove. In Portuguese, the word mangrove is used for individual plant species, while mangal is used for the forest community. In English, mangrove is defined as trees that grow in coastal areas or other associated plants. Other terms used to refer to mangrove forests include coastal woodland, mangal, and tidal forest. Mangroves are a coastal tropical vegetation community that lives in estuaries, rivers, lagoons, and intertidal zones with muddy or sandy-mud substrate. Mangroves are classified as higher plants that have the potential for abundant organic matter content, nitrogen, and sulfur compounds used by microorganisms for growth.

Mangrove ecosystems are classified as intertidal ecosystems where there is strong interaction between seawater, brackish water, rivers, and terrestrial areas. Mangroves live in tropical and subtropical climate zones and play a role in ecological, social, and economic systems. Mangrove ecosystems also play an important role as habitats for various organisms. Mangrove forests generally have vegetation that is physiologically adaptable to high salinity, structure, tidal conditions, and substrate composition, such as Rhizophora sp. and Avicennia alba. Mangroves consist of major mangroves, minor mangroves, and associated mangroves. Mangrove genera that grow on alluvial muddy soil in river estuaries influenced by tides include Avicennia, Sonneratia, Rhizophora, Bruguiera, Ceriops, Lumnitzera, Xylocarpus, Aegiceras, Nypa, Scyphyphora, and Excoecaria

Tropical Biology

Indonesia's tropical region geographically covers areas located between the Northern Tropic and 23°27’ South Latitude. The tropics are regions located between the 18°C isotherm of the coldest month. Overall, the tropics cover 30% of the Earth's surface. Tropical forests are forests located in tropical regions. Tropical rainforests are one of the oldest forest vegetation types that have covered much of the land. Tropical rainforest ecosystems exist in areas with climate types A and B (according to the Schmidt and Ferguson climate classification), or it can be said that this ecosystem type is found in areas that are always wet, in areas with Podsol, Latosol, Alluvial, and Regosol soil types with good drainage, and located far from the coast. Tropical rainforest stands are dominated by evergreen trees. The diversity of plant and animal species in tropical rainforests is very high. The number of tree species found in tropical rainforests is greater than that found in other ecosystems.

Biodiversity, or the diversity of living organisms, comes from various sources within an ecosystem. An ecosystem is a collection of organisms, both plants and animals, that interact with each other and with their surrounding environment. Biodiversity is the term used for the diversity of natural resources, including the number and frequency of ecosystems, species, and genes in a given place. Basically, diversity describes a varied condition of an object that occurs due to differences in size, shape, texture, and quantity, while the word "biological" means something that is alive. Biodiversity can be defined as the diversity or variety of living organisms that can occur as a cause and effect. Differences include variations in shape, size, color, texture, appearance, and also their characteristics. Biodiversity is also often known as biodiversity.

Biodiversity is a level that exists on Earth and this becomes a benchmark or measure for determining environmental health. Biodiversity in tropical ecosystems has a higher number than biodiversity in cold environments. This condition is caused by climate or weather because biodiversity is a function of climate. Diversity can also be caused by genetic variation or gene structure within a species of living organism. Genes themselves are hereditary trait carriers that can be found in chromosomes. Each gene sequence will give an appearance, both anatomical and physiological, to each organism. If the sequence is different, then the appearance will also be different in one trait or even overall. This diversity is quite easy to recognize by characteristics that have variations, the same scientific name, and morphological differences that are not too striking. Usually, genetic-level biodiversity is called a variety.

Escherichia coli

Escherichia coli is a pathogenic bacterium that lives in the intestines of humans and animals and plays a role in maintaining a healthy digestive system. This bacterium is also found in water and food, as are non-pathogenic strains of E. coli. Pathogenic strains, such as enterotoxigenic E. coli (EPEC), produce shiga toxin, which is an indicator of water pollution and invades the epithelial cells of the small intestine. The presence of E. coli in aquatic environments indicates contamination by waste or animal feces carried in the water.Escherichia coli is a type of bacteria belonging to the coliform family that normally lives in human and animal feces, therefore it is also called fecal coliform. E. coli is a Gram-negative, rod-shaped, non-spore-forming bacterium. E. coli is commonly found in water as a source of microbial pollution. This bacterium forms rods in chains with a length of approximately 2 micrometers and a diameter of 0.5 micrometers. This bacterium has Bacillus forms include monobacilli, diplobacilli, or streptobacilli, and do not form spores or capsules. The volume of E. coli generally ranges from 0.6-0.7 m3. Inappropriate E. coli culture can result in long filaments, rarely capsules, and motile E. coli strains.

E. coli bacteria have round, convex, smooth colonies with distinct edges. E. coli is classified as an opportunistic bacterium commonly found in the human large intestine as normal flora. E. coli motility can be either motile or non-motile. This pathogenic bacterium thrives at temperatures between 8-46°C, but its optimal temperature is 37°C (Arivo and Annissatussholeha, 2017). This temperature range allows E. coli to grow well in the human digestive tract. E. coli is known as a bacteria that causes diarrhea and digestive tract disorders. Not all E. coli are dangerous, but only a small number cause disease if their growth is uncontrolled. E. coli is generally harmless and can benefit humans by playing a role in the production of vitamin K. The presence of E. coli as part of the intestinal flora actually prevents the growth of other potentially harmful bacteria in the intestine.

Actinomycetes

Actinomycetes are microorganisms native to the sea and can be found on the surface of seawater, the seabed, in sediments, coral reefs, and in soil. Actinomycetes are prokaryotic, like bacteria, but possess mycelium and are classified as microbes with the potential to produce secondary metabolites.

Actinomycetes form symbiotic relationships with sponges on the outside of the body (extracellular exosymbiosis), inside the sponge (extracellular endosymbiosis), in the cytoplasm (intracellular symbiosis), and in the cell nucleus (intranuclear symbiosis). Actinomycetes are capable of producing bioactive compounds from antibiotics (70%), fungi (20%), and bacteria (10%). This type of microbe has been widely used in the pharmaceutical, animal feed, fisheries, and other industries. Commercial products that utilize actinomycete secondary metabolites include tetracycline, erythromycin, vancomycin, and streptomycin.

Bio-Active Compounds of Sponge

Sponges are marine invertebrates that possess more than 20 categories of bioactive compounds, including antibiotics, antivirals, anti-inflammatories, anticancer, antileukemic, insecticidal, antihelminthic, and cytotoxins, making them attractive for development. Nutritionally, sponges are more suitable as microbial niches than nutrient-poor seawater. The interaction between bacteria and sponges is called mutualistic symbiosis, producing bioactive compounds. Sponges with high microbial abundance are called High-Microbial-Abundance (HMA), while sponges with low microbial abundance are called Low-Microbial-Abundance (LMA). The microbes that symbiotically interact with sponges, known as secondary metabolite producers, are members of the Actinobacteria group.