Aquatic Actinomycetes: A Critical Survey of the Occurrence, Growth and Role of Actinomycetes in Aquatic Habitats

Cross, T.

doi:10.1111/j.1365-2672.1981.tb04245.x

Cited by 119 publications

(62 citation statements)

References 63 publications

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“…Most of the information on the occurrence of Micromonospora spp. in aquatic habitats was published over 20 years ago (4,10,12). The presence of micromonosporas along with other actinomycetes and their interaction with fungi in submerged macrophytes and decomposing leaf matter have been investigated in some more recent studies (18,27,28), whereas others have focused on the diversity and isolation of members of the Micromonosporaceae from different habitats such as marine sediments and Antarctic rocks (7)(8)(9)20).…”

Section: Vol 74 2008 Cellulose Degradation By Micromonosporas 7081mentioning

confidence: 99%

Cellulose Degradation by Micromonosporas Recovered from Freshwater Lakes and Classification of These Actinomycetes by DNA Gyrase B Gene Sequencing

Menezes

Lockhart

Cox

et al. 2008

Appl Environ Microbiol

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A number of Micromonospora strains isolated from the water column, sediment, and cellulose baits placed in freshwater lakes were shown to be able to degrade cellulose in lake water without any addition of nutrients. A selective isolation method was also developed to demonstrate that CFU arose from both spores and hyphae that inhabit the lake environment. Gyrase B gene sequencing performed on the isolates identified a number of new centers of variation within Micromonospora, but the most actively cellulolytic strains were recovered in a single cluster that equated with the type species of the genus, M. chalcea.Cellulose, the most abundant form of fixed carbon in the biosphere, is insoluble and its efficient degradation is largely restricted to those specific groups of microorganisms that are able to produce multiple cellulases (14). Many microorganisms can attack amorphous cellulose to some degree, but relatively few taxa can completely degrade highly crystalline cellulose, of which the best example is cotton. In terrestrial environments, cellulose tends to be highly lignified and more difficult to degrade, and both fungi (14) and actinomycetes (15) can obtain access to cellulose in woody tissue due to their hyphal growth form. In contrast, little is known about the contributions of different groups of microorganisms to cellulose degradation in aquatic ecosystems.Micromonosporas are a group of actinomycetes that are usually present in large numbers in soil but are well adapted to water dispersal, as evidenced by the absence of aerial hyphae and production of hydrophilic spores. They can be readily recovered from aquatic environments, especially lake sediments (4), but it is important that their presence is not equated with activity, for micromonosporas produce enormous numbers of spores that can accumulate and remain viable in lakes. Although they grow slowly and can be easily missed or outcompeted in culture-based surveys (27), the ability to degrade complex polysaccharides such as cellulose and chitin is regarded as common among the micromonosporas (12). Against this background, the study reported here concentrates on determining the presence, growth, diversity, and cellulolytic ability of Micromonospora strains colonizing cellulose baits placed in freshwater lakes.Micromonosporas were recovered from two lakes of contrasting trophic status in the English Lake District: Esthwaite Water and Priest Pot. The former is 15 m in depth, 113 ha in area, and eutrophic (average chlorophyll a concentration, 54 g liter Ϫ1 ) (5). Priest Pot is 3.5 m deep, 1 ha in area, and is hypereutrophic (average chlorophyll a concentration, 300 g liter Ϫ1 ) (3). Stratification leading to the formation of an anaerobic zone occurs in the summer months in both lakes but is more persistent in Priest Pot, which is sheltered and has steep oxygen and temperature gradients. Cotton was dewaxed by repeated chloroform-ethanol extraction (29) in a Soxhlet apparatus (Quickfit; SciLabware, Stone, England) prior to use as baits for the recovery of cell...

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Section: Vol 74 2008 Cellulose Degradation By Micromonosporas 7081mentioning

confidence: 99%

Cellulose Degradation by Micromonosporas Recovered from Freshwater Lakes and Classification of These Actinomycetes by DNA Gyrase B Gene Sequencing

Menezes

Lockhart

Cox

et al. 2008

Appl Environ Microbiol

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“…In fact, the distributions of actinomycetes in the sea remain largely undescribed, and even today, conclusive evidence that these bacteria play important ecological roles in the marine environment has remained elusive. Speculation regarding the existence of indigenous populations of marine actinomycetes arises because these bacteria produce resistant spores that are known to be transported from land into the sea where they can remain viable but dormant for many years (2,3,5). Thus, it has been frequently assumed that actinomycetes isolated from marine samples are merely of terrestrial origin.…”

mentioning

confidence: 99%

Widespread and Persistent Populations of a Major New Marine Actinomycete Taxon in Ocean Sediments

Mincer

Jensen

Kauffman

et al. 2002

Appl Environ Microbiol

520

416

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A major taxon of obligate marine bacteria within the order Actinomycetales has been discovered from ocean sediments. Populations of these bacteria (designated MAR 1) are persistent and widespread, spanning at least three distinct ocean systems. In this study, 212 actinomycete isolates possessing MAR 1 morphologies were examined and all but two displayed an obligate requirement of seawater for growth. Forty-five of these isolates, representing all observed seawater-requiring morphotypes, were partially sequenced and found to share characteristic small-subunit rRNA signature nucleotides between positions 207 and 468 (Escherichia coli numbering). Phylogenetic characterization of seven representative isolates based on almost complete sequences of genes encoding 16S rRNA (16S ribosomal DNA) yielded a monophyletic clade within the family Micromonosporaceae and suggests novelty at the genus level. This is the first evidence for the existence of widespread populations of obligate marine actinomycetes. Organic extracts from cultured members of this new group exhibit remarkable biological activity, suggesting that they represent a prolific resource for biotechnological applications.The recently proposed class Actinobacteria (20) is comprised of high-GϩC-content gram-positive bacteria and includes the actinomycetes (order Actinomycetales), whose members have an unparalleled ability to produce diverse secondary metabolites. These bacteria are primarily saprophytic and are best known from soils where they contribute significantly to the turnover of complex biopolymers, such as lignocellulose, hemicellulose, pectin, keratin, and chitin (27). Additionally, nitrogen-fixing actinomycetes of the genus Frankia have one of the broadest host ranges known, forming root nodule symbioses in more than 200 species of flowering plants (7).Despite their importance in soil ecology, actinomycetes are best known as a source of antibiotics. This became apparent in 1940, following Selman Waksman's seminal discovery of actinomycin (24), and was fully realized by the 1980s, when actinomycetes accounted for almost 70% of the world's naturally occurring antibiotics (15). In the past two decades, however, there has been a decline in the discovery of new lead compounds from common soil-derived actinomycetes as culture extracts yield unacceptably high numbers of previously described metabolites. For this reason, the cultivation of rare or novel actinomycete taxa has become a major focus in the search for the next generation of pharmaceutical agents (2).It is interesting that the world's oceans, which cover 70% of the earth's surface and include some of the most biodiverse ecosystems on the planet, have not been widely recognized as an important resource for novel actinomycetes. In fact, the distributions of actinomycetes in the sea remain largely undescribed, and even today, conclusive evidence that these bacteria play important ecological roles in the marine environment has remained elusive. Speculation regarding the existence of indigenous populatio...

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“…The few reports on aquatic Actinomycetes (e.g. Willoughby 1969, Cross 1981, Gavrishova 1981) mostly deal with their presence in littoral zones of reservoirs. More recently, the objective has been to discover novel enzymes and metabolites from these organisms (Takizawa et al 1993, Jiang & Xu 1996.…”

Section: Reed and Macrophytes Decompositionmentioning

confidence: 99%

Fungi in lake ecosystems

Wurzbacher¹,

Bärlocher²,

Grossart³

2010

Aquat. Microb. Ecol.

208

170

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This review highlights the presence and ecological roles of fungi in lakes, and aims to stimulate research in aquatic mycology. In the study of lentic systems, this field is an almost completely neglected topic and, if considered at all, has often been restricted to specific groups of fungi, such as yeasts, filamentous fungi (e.g. aquatic hyphomycetes), or phycomycetes (an obsolete taxonomic category that included various fungal and fungal-like organisms). We document that aquatic fungi are common in various lentic habitats. They play potentially crucial roles in nutrient and carbon cycling and interact with other organisms, thereby influencing food web dynamics. The development and application of molecular methods have greatly increased the potential for unraveling the biodiversity and ecological roles of fungi in lake ecosystems. We searched the literature for reports on all fungi occurring in lake ecosystems. The present study summarizes information on the highly diverse mycoflora in lake microhabitats and highlights the main processes they influence. We also point out ecological niches of fungi in lakes that have been examined only superficially or ignored completely. We demonstrate that we now have the methodology to perform systematic studies to finally fill in some of the large gaps in this field.

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Aquatic Actinomycetes: A Critical Survey of the Occurrence, Growth and Role of Actinomycetes in Aquatic Habitats

Cited by 119 publications

References 63 publications

Cellulose Degradation by Micromonosporas Recovered from Freshwater Lakes and Classification of These Actinomycetes by DNA Gyrase B Gene Sequencing

Cellulose Degradation by Micromonosporas Recovered from Freshwater Lakes and Classification of These Actinomycetes by DNA Gyrase B Gene Sequencing

Widespread and Persistent Populations of a Major New Marine Actinomycete Taxon in Ocean Sediments

Fungi in lake ecosystems

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