Members Of Phylum Actinobacteria Research Articles

Antifungal activity of rare actinobacterium isolated from forest soil

Prolonged use of antifungal drugs has led to the emergence of drug resistant fungal pathogens that pose serious threat to public health and challenge to researchers for discovering novel antifungal agents. Natural products from the members of phylum actinobacteria are the promising source of antibiotics including antifungal agents. Twenty-seven morphologically different actinobacterial cultures were isolated from the forest soils of Sabarimala, Kerala and Lucknow, Uttar Pradesh. Actinobacterial strain LA34 showed promising antifungal activity when screened against Candida albicans and Cryptococcus neoformans, hence selected as potential strain. Antifungal compounds were produced from the strain LA34 using agar surface fermentation and its extraction was done using ethyl acetate and methanol. Results of cultural, microscopic and physiological characteristics as well as cell wall amino acid and sugars analysis revealed that the strain LA34 was nonstreptomyces or rare actinobacterium. Various carbon sources, nitrogen sources and minerals were found to influence antifungal compound production by the strain LA34. The present study concluded that the rare actinobacterial strain LA34 isolated from Lucknow forest soil is a promising source for the isolation of antifungal compounds.

Cave Actinobacteria as Producers of Bioactive Metabolites.

Recently, there is an urgent need for new drugs due to the emergence of drug resistant pathogenic microorganisms and new infectious diseases. Members of phylum Actinobacteria are promising source of bioactive compounds notably antibiotics. The search for such new compounds has shifted to extreme or underexplored environments to increase the possibility of discovery. Cave ecosystems have attracted interest of the research community because of their unique characteristics and the microbiome residing inside including actinobacteria. At the time of writing, 47 species in 30 genera of actinobacteria were reported from cave and cave related habitats. Novel and promising bioactive compounds have been isolated and characterized. This mini-review focuses on the diversity of cultivable actinobacteria in cave and cave-related environments, and their bioactive metabolites from 1999 to 2018.

Actinobacteria for sustainable agriculture

Actinobacteria is a phylum and class of Gram-positive bacteria. The phylum Actinobacteria are classified into six classes namely Acidimicrobiia, Actinobacteria, Coriobacteriia, Nitriliruptoria, Rubrobacteria and Thermoleophilia. Members of phylum Actinobacteria are ubiquitous in nature. Actinobacteria can be utilized as biofertilizers for sustainable agriculture as they can enhance plant growth and soil health though different plant growth promoting attributes such as solubilization of phosphorus, potassium and zinc, production of Fe-chelating compounds, phytohormones hormones such indole acetic acids, cytokinin, and gibberellins as well as by biological nitrogen fixation. The Actinobacteria also plays an important role in mitigation of different abiotic stress conditions in plants. The members of phylum Actinobacteria such as Actinomyces, Arthrobacter, Bifidobacterium, Cellulomonas, Clavibacter, Corynebacterium, Frankia, Microbacterium, Micrococcus, Mycobacterium, Nocardia, Propionibacterium, Pseudonocardia, Rhodococcus, Sanguibacter and Streptomyces exhibited the multifarious plant growth promoting attributes and could be used as biofertilizers for crops growing under natural as well as under the abiotic stress conditions for plant growth and soil health for sustainable agriculture.

Microbial community diversity and composition across a gradient of soil acidity in spruce–fir forests of the southern Appalachian Mountains

Anthropogenic deposition of sulfur (S) and nitrogen (N) contributes substantially to soil acidity in some forest regions and hence studies have focused on modeling and quantifying depositions in landscapes. The resulting acidity can change the soil chemical balance, nutrient availability, microbial communities, and at a broader scale, ecosystem functioning. In this study, a 16S PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) approach was used to measure the bacterial diversity and identify the dominant bacterial species along a soil acidity gradient in high elevation spruce–fir forests of Great Smoky Mountains National Park (GSMNP). Sample sites were selected based upon modeled S deposition class (6–14, 15–23, 23–32, and 33–41kgha−1). Collected soils were analyzed for pH, C, N, Ca, Al, S, CEC, and base saturation. Average soil pH in the O, A, and B horizons were 3.6, 3.6 and 3.9, respectively. Modeled S deposition was found to be an unreliable predictor of soil S content as well as most other soil chemical properties. DGGE profiles of bacterial partial 16S rRNA genes revealed minor differences in bacterial diversity while communities were similar, dominated by members of phylum Actinobacteria, Acidobacteria, Planctomycetes, Proteobacteria, and Chloroflexi. Dominance of acidophilic bacterial species, often found in highly acidic environment such as acid-mine drainage and sphagnum bogs, suggests that the poorly buffered soils that are endemic to southern Appalachian spruce–fir forests are saturated with acidity. Our results suggest that stricter air quality standards have not resulted in shift to less acid-tolerant bacteria.