Isolation, identification and hydrolytic enzymes production of aerobic heterotrophic bacteria from two Antarctic islands.
Tomova, I., Gladka, G., Tashyrev, A. & Vasileva-Tonkova, E. (2014). International Journal of Environmental Sciences, 4(5), 614-625.
The microbial communities in some Antarctic regions still have not extensively investigated. In the present study, we isolated 24 bacterial strains under aerobic conditions from terrestrial samples at two locations in maritime Antarctica: Deception Island and Galindez Island. Phylogenetic analysis based on the 16S rRNA gene sequencing revealed affiliation of the Antarctic isolates to Gammaproteobacteria (54.2%), Betaproteobacteria (8.3%), Firmicutes (20.8%), and Actinobacteria (16.7%). The majority of isolates (92%) are psychrotolerant, and 75% are halotolerant. About 63% of isolated Antarctic bacteria were able to produce hydrolytic enzymes suggesting important role of the strains in carbon and nitrogen cycling in their habitats. Among isolates, producers of proteases (58.3%), ureases (45.8%), polygalacturonases (41.6%), β-glucosidases (33.3%), phytases (20.8%) and ribonucleases (16.6%) were detected. The results revealed higher potential of isolates from Deception Island to produce hydrolytic enzymes than those from Galindez Island. To the best of our knowledge, this is the first report for polygalacturonase production by Antarctic bacteria and β-glucosidase production by culturable Antarctic Burkholderia strain. The results obtained contribute to better understanding of the diversity of culturable heterotrophic bacteria in maritime Antarctica and their potential for production of hydrolytic enzymes allowing detection of promising psychrotolerant producers of industrially important enzymes.
Marinimicrobium haloxylanilyticum sp. nov., a new moderately halophilic, polysaccharide-degrading bacterium isolated from Great Salt Lake, Utah.
Møller, M. F., Kjeldsen, K. U. & Ingvorsen, K. (2010). Antonie van Leeuwenhoek, 98(4), 553-565.
A new moderately halophilic, strictly aerobic, Gram-negative bacterium, strain SX15T , was isolated from hypersaline surface sediment of the southern arm of Great Salt Lake (Utah, USA). The strain grew on a number of carbohydrates and carbohydrate polymers such as xylan, starch, carboxymethyl cellulose and galactomannan. The strain grew at salinities ranging from 2 to 22% NaCl (w/v). Optimal growth occurred in the presence of 7–11% NaCl (w/v) at a temperature of 35°C and a pH of 6.7–8.2. Major whole-cell fatty acids were C16:0 (30.5%), C18:0 (14.8%), C18:1ϖ7c(13.1%) and C12:0 (7.8%). The G+C content of the DNA was 60 ± 0.5 mol%. By 16S rRNA gene sequence analysis, strain SX15T was shown to be affiliated to members of the gammaproteobacterial genus Marinimicrobium with pair wise identity values of 92.9–94.6%. The pheno- and genotypic properties suggest that strain SX15T represents a novel species of the genus Marinimicrobium for which the name Marinimicrobium haloxylanilyticum is proposed. The type strain is SX15T (= DSM23100T = CCUG 59572T).
Evolutionary transitions in enzyme activity of ant fungus gardens.
De Fine Licht, H. H., Schiøtt, M., Mueller, U. G. & Boomsma, J. J. (2010). Evolution, 64(7), 2055-2069.
Fungus-growing (attine) ants and their fungal symbionts passed through several evolutionary transitions during their 50 million year old evolutionary history. The basal attine lineages often shifted between two main cultivar clades, whereas the derived higher-attine lineages maintained an association with a monophyletic clade of specialized symbionts. In conjunction with the transition to specialized symbionts, the ants advanced in colony size and social complexity. Here we provide a comparative study of the functional specialization in extracellular enzyme activities in fungus gardens across the attine phylogeny. We show that, relative to sister clades, gardens of higher-attine ants have enhanced activity of protein-digesting enzymes, whereas gardens of leaf-cutting ants also have increased activity of starch-digesting enzymes. However, the enzyme activities of lower-attine fungus gardens are targeted primarily toward partial degradation of plant cell walls, reflecting a plesiomorphic state of nondomesticated fungi. The enzyme profiles of the higher-attine and leaf-cutting gardens appear particularly suited to digest fresh plant materials and to access nutrients from live cells without major breakdown of cell walls. The adaptive significance of the lower-attine symbiont shifts remains unclear. One of these shifts was obligate, but digestive advantages remained ambiguous, whereas the other remained facultative despite providing greater digestive efficiency.
Patterns of functional enzyme activity in fungus farming ambrosia beetles.
Licht, H. H. D. F. & Biedermann, P. H. W. (2012). Frontiers in Zoology, 9(1), 13.
Introduction: In wood-dwelling fungus-farming weevils, the so-called ambrosia beetles (Curculionidae: Scolytinae and Platypodinae), wood in the excavated tunnels is used as a medium for cultivating fungi by the combined action of digging larvae (which create more space for the fungi to grow) and of adults sowing and pruning the fungus. The beetles are obligately dependent on the fungus that provides essential vitamins, amino acids and sterols. However, to what extent microbial enzymes support fungus farming in ambrosia beetles is unknown. Here we measure (i) 13 plant cell-wall degrading enzymes in the fungus garden microbial consortium of the ambrosia beetle Xyleborinus saxesenii, including its primary fungal symbionts, in three compartments of laboratory maintained nests, at different time points after gallery foundation and (ii) four specific enzymes that may be either insect or microbially derived in X. saxesenii adult and larval individuals. Results: We discovered that the activity of cellulases in ambrosia fungus gardens is relatively small compared to the activities of other cellulolytic enzymes. Enzyme activity in all compartments of the garden was mainly directed towards hemicellulose carbohydrates such as xylan, glucomannan and callose. Hemicellulolytic enzyme activity within the brood chamber increased with gallery age, whereas irrespective of the age of the gallery, the highest overall enzyme activity were detected in the gallery dump material expelled by the beetles. Interestingly endo-β-1,3(4)-glucanase activity capable of callose degradation was identified in whole-body extracts of both larvae and adult X. saxesenii, whereas endo-β-1,4-xylanase activity was exclusively detected in larvae. Conclusion: Similar to closely related fungi associated with bark beetles in phloem, the microbial symbionts of ambrosia beetles hardly degrade cellulose. Instead, their enzyme activity is directed mainly towards comparatively more easily accessible hemicellulose components of the ray-parenchyma cells in the wood xylem. Furthermore, the detection of xylanolytic enzymes exclusively in larvae (which feed on fungus colonized wood) and not in adults (which feed only in fungi) indicates that only larvae (pre-) digest plant cell wall structures. This implies that in X. saxesenii and likely also in many other ambrosia beetles, adults and larvae do not compete for the same food within their nests - in contrast, larvae increase colony fitness by facilitating enzymatic wood degradation and fungus cultivation.
The use of plant cell wall degrading enzymes from a newly isolated Penicillium ochrochloron Biourge for viscosity reduction in ethanol production with fresh sweet potato tubers as feedstock.
Huang, Y., Jin, Y., Shen, W., Fang, Y., Zhang, G. & Zhao, H. (2014). Biotechnology and Applied Biochemistry, 61(4), 480-491.
Penicillium ochrochloron Biourge, which was isolated from rotten sweet potato, can produce plant cell wall degrading enzymes (PCWDEs) with high viscosity reducing capability for ethanol production using fresh sweet potato tubers as feedstock. The enzyme preparation was characterized by a broad enzyme spectrum including 13 kinds of enzymes with the activity to hydrolyze cellulose, hemicellulose, pectin, starch and protein. The maximum viscosity reducing capability was observed when the enzyme preparation was obtained after five days fermentation using 20 g/L corncob as sole carbon source, 4.5 g/L NH4NO3 as sole nitrogen source, and an initial medium pH of 6.5. The sweet potato mash treated with the enzyme preparation exhibited much higher fermentation efficiency (92.58%) compared with commercial cellulase (88.06%) and control (83.5%). The enzyme production was then scaled up to 0.5, 5, and 100 L, and the viscosity reducing rates were found to be 85%, 90%, and 91%, respectively. Thus, P. ochrochloron Biourge displays potential viscosity reducing capability for ethanol production.
Metatranscriptomics Reveals the Functions and Enzyme Profiles of the Microbial Community in Chinese Nong-Flavor Liquor Starter.
Huang, Y., Yi, Z., Jin, Y., Huang, M., He, K., Liu, D., Luo, H., Zhao, D., He, H., Fang, Y. & Zhao, H. (2017). Frontiers in Microbiology, 8, 1747.
Chinese liquor is one of the world's best-known distilled spirits and is the largest spirit category by sales. The unique and traditional solid-state fermentation technology used to produce Chinese liquor has been in continuous use for several thousand years. The diverse and dynamic microbial community in a liquor starter is the main contributor to liquor brewing. However, little is known about the ecological distribution and functional importance of these community members. In this study, metatranscriptomics was used to comprehensively explore the active microbial community members and key transcripts with significant functions in the liquor starter production process. Fungi were found to be the most abundant and active community members. A total of 932 carbohydrate-active enzymes, including highly expressed auxiliary activity family 9 and 10 proteins, were identified at 62°C under aerobic conditions. Some potential thermostable enzymes were identified at 50, 62, and 25°C (mature stage). Increased content and overexpressed key enzymes involved in glycolysis and starch, pyruvate and ethanol metabolism were detected at 50 and 62°C. The key enzymes of the citrate cycle were up-regulated at 62°C, and their abundant derivatives are crucial for flavor generation. Here, the metabolism and functional enzymes of the active microbial communities in NF liquor starter were studied, which could pave the way to initiate improvements in liquor quality and to discover microbes that produce novel enzymes or high-value added products.