Journal of Microbial Biology
Year:2017 | Volume:5 | Issue:20 |Papers Count:7

Introduction: Microbial lipids attract attention of many researchers due to their therapeutic effects. The goal of this study is the production and optimization of lipids and fatty acids in Mortierella vinacea by applying different media to achieve invaluable fatty acids in pharmaceutical and food industry.Materials and methods: Mortierella vinacea was cultured on potato dextrose agar. Then the spores were inoculated to the production medium. After 72 hours, the lipids were extracted and they were analyzed by gas chromatography. To optimize lipid and important fatty acids production in medium, various carbon and nitrogen sources were substituted with glucose and yeast extract respectively.Results: The effect of some carbon and nitrogen sources on biomass, lipid and fatty acids production were assayed. The highest level of lipid production was in a medium which contains lactose and yeast extract (26.66%). Linoleic acid was only produced in presence of lactose and yeast extract (25.7%). While, M. vinacea yielded the highest level of linoleic acid (52.76%) in a medium containing peptone, linolenic acid was achieved only in presence of lactose and triptone.Discussion and conclusion: In this study, lactose as a carbon source was the most effective one in the production of lipids. In addition, linoleic acid was produced in presence of lactose, so lactose was selected as the best carbon source. Peptone and triptone as a nitrogen source were chosen for the production of linoleic acid and linolenic acid in M. vinacea respectively. All of these findings reveal that Mortierella strain is a potential candidate for enhancement of linoleic acid and linolenic acid production. Furthermore, this simple media can be used in production of linoleic acid and linolenic acid for industrial goals in large scales.

Introduction: Human gastrointestinal disease caused by verotoxigenic Escherichia coli has been diagnosed for recent decades. Escherichia coli O157: H7 is the most important serotype of verotoxigenic Escherichia coli that cause hemolytic uremic syndrome and hemorrhagic colitis in humans. This study was conducted to determine the occurrence of verotoxigenic E. coli and antibiotic resistance of the isolates from vegetables.Materials and methods: A total of 500 fresh vegetable samples were collected randomly from retail shops in Shahrekord, Iran. E. coli was isolated and identified using bacteriological and biochemical tests. PCR method was used to identify the rbfE, stx1, stx2 and eae genes. Also, antibiotic resistance of the isolates was determined by disk diffusion method.Results: The results represented that among 25 isolates possess virulence genes, 40, 12 and 4% of the isolates contained eaeA, STx2, and both genes, respectively. But none of them contained H7, STx1, and rfbE genes. The antibiotic resistance pattern demonstrated that the isolates were highly resistant to Gentamycin and cefotoxime.Discussion and conclusion: The results of this study showed that the presence of verotoxigenic E.coli in vegetables; and high resistance of the isolates to antibiotics could be hazardous for public health.

Introduction: Microbial extracellular alkaline proteases are one of the most important industrial enzymes with a wide range of applications in various industries. In the present study, the production of an alkaline protease by Bacillus pseudofirmus MSB4 was evaluated using response surface methodology (RSM).Materials and methods: Four significant independent variables were selected, based on the results of one-factor-at-a-time (OFAT) approach (xylose concentration, beef extract concentration, pH and temperature), for rotatable central composite design (RCCD) to analyze the response pattern and to establish a model. The design consisted of total 30 runs, at five levels for each factor, with four replications of the center points. In addition, the presence of extracellular alkaline protease genes was evaluated by using PCR.Results: Maximum protease production (185.397 U/ml), 2.2 times higher than that of OFAT method and 3.7 times higher than the unoptimized conditions, was obtained by using 3% w/v beef extract, at pH 9 and 37oC according to the results of RCCD. Furthermore, the genes sub I, II and apr with the expected size (319, 486 and 194 bp, respectively) corresponding to the extracellular alkaline serine protease and metalloprotease were detected in MSB4 by using PCR.Discussion and conclusion: The experimental data well fitted the model (Adj R2: 0.9982) and the established quadratic model has a great ability to predict responses for new observations (Pred R2: 0.9967). The results showed that the OFAT and RSM strategies were a useful screening and optimization method for enhancing protease production of MSB4, respectively.

Introduction: Algae has many applications in terms of ecology, biodiversity, agriculture, medicine, biotechnology, industry, etc. They are potent organisms in bio-active compound production, bioremediation and primary producer. Therefore, it is important to discover local strains with biotechnological and ecological applications.Materials and methods: Soil and water samples were collected from different sites of Khark Island (Persian Gulf). The samples were cultivated and purified using different techniques. Seven different antibiotics together with other physical methods used to purify the isolates.Results: Throughout the project 7 strains including 2 eukaryotic algae and 5 cyanobacteria have been isolated. Imipenem and cycloheximide were the best antibiotics for purification of cultures. Three of isolates were morphologically similar to Arthronema africanum, Pseudanabaena teremula, Anabaenopsis sp. However, they have some different characteristics which according to the present identification keys it is not possible to identify their identity (they have nominated Kh.C.d2, Kh.T.1 and Kh.T.2).Discussion and conclusion: According to the results, isolated strains were identified at the genus level based on morphology characters; therefore the complementary examinations such as molecular identification, ITS, 18s rRNA, 16s rRNA and sequencing can help to approve the strains identity. Upon approval of the new strains account for morphological traits are necessary for their easy identification. The Imipenem antibiotic is the best for eukaryotic algae purification and Cycloheximide is suitable for prokaryotic algae (cyanobacteria) purification.

Introduction: The study of symbiotic relationship between arbuscular mycorrhizal fungi (AMF) and medicinal plants is very important. Information about the symbiosis of medicinal plant species with AMF in the semi-arid regions of Iran is rare. This information allows increasing knowledge of the biology and ecology of these plant species.Materials and methods: The existence of AM symbiosis in 48 medicinal plant species (belonging to 9 families) was studied by root staining. Soil around the root of each species was sampled and analyzed for all soil properties which may be interrelated to AM symbiosis. The importance of different soil properties in AMF and plant biological relationship and the dependency of root colonization and spore formation by AMF on soil properties were statistically analyzed.Results: Among them Lepidium sativum, Brassica oleracea, Cheiranthus cheiri, Beta vulgaris, Spinacia oleracea, Malva sylvestris, Zygophyllum fabago, Arctium Lappa have not been colonized by AM fungi. Colonization and spore density of perennial plants were slightly higher than those of annual plants and were varied among different plant families. Soil texture and available phosphorous were the most important soil properties affecting fungal root colonization and spore numbers.Discussion and conclusion: Although in accordance with other researches, most of the medicinal plants from Brassicaceae family had no mycorrhizal symbiosis, a few of them had this type of symbiosis. Dependency of spore formation by AM fungi on soil properties was higher than dependency of root colonization percentage on soil properties. Increasing root colonization and spore numbers with increasing the percentage of sand and decreasing the percentage of clay and available phosphorous in soils show that plants are more depended on mycorrhizal symbiosis in hard environments and less productive soils.

Introduction: Tannins (tannic acid) are toxic, high molecular weight and water- soluble polyphenols that are present in many plants such as pistachio and its by- products. Wide ranges of microorganisms including bacteria tolerate tannin and degrade it. The aim of this study was to isolate and characterize tannin- tolerant bacteria from pistachio soft hulls (P- SH) and feces of goat before and after feeding on this by- product as tannin rich diet.Materials and methods: Tannin tolerant bacteria were isolated from enrichment cultures of samples in medium containing tannic acid as a sole source of carbon and energy. Tannin hydrolyzing ability of isolates was confirmed by observation of clear zones around the colonies. The increasing concentrations of tannin on minimal salt medium (MSM) agar plates were used to test the maximum tolerable concentrations (MTCs). Furthermore, in the supplemented media tannin concentrations were measured by bovine serum albumin (BSA) precipitation assay during time intervals.Results: Tannin- degrading bacterial population of P- SH was about only 10.3% of total population. More than 50 percent of tannin degrading strains were isolated from goat feces after grazing on tannin rich diet. Isolated bacteria were Gram- negative and positive rod species belonging to Klebsiella, Pseudomonas, Bacillus, Escherichia and Enterobacter genera. Among the isolated bacteria 71.4% could tolerate the concentration of 64 g/l of tannin in their media while only 7.2% were able to tolerate the maximum tannin concentration of 16 g/l. Bacterial isolates of goat feces could degrade tannin more than 72% after 72 h of incubation. In the case of soft P- SH isolates, the biodegradation percentage was between 17- 75%.Discussion and conclusion: Feeding of tannin rich diet induced a shift in digestive system microbial profile with increased population of tannin tolerant bacteria. The ability of isolated strains provides novel insights for the role they can play in composting tannin containing wastes.

Introduction: Catechol is a common intermediate compound in aromatic degradation process. Some microorganisms have this potentiality to degrade aromatic hydrocarbons by catechol dioxygenases to less toxic compounds with ability of entering the tricarboxylic acid cycle. In the present study, the catechol oxygenase activity was measured for 12 crude oil degrader bacteria.Materials and methods: Catechol oxygenase activity of two enzymes includes catechol 1, 2 dioxygenase and catechol 2, 3 dioxygenase were determined using spectrophotometer at 260 nm and 375 nm, respectively.Results: The highest enzyme activity for catechol 1, 2 dioxygenase by Bacillus cereus UKMP-6G was (0.07 U/mL) and about catechol 2, 3 dioxygenase was 0.031 U/mL by Rhodococcus ruber UKMP-5M during the first minute of incubation. Catechol 1, 2 dioxygenase and catechol 2, 3 dioxygenase followed the ortho and meta pathway, respectively.Discussion and conclusion: The enzyme assay results showed that among 12 examined bacteria, only R. ruber UKMP-5M has the ability to use meta pathway for degradation and produce 2-hydroxymuconic acid. The other isolates use ortho pathway and create cis, cis -muconic acid.