That major flows of energy occur along detrital pathways in all ecosystems is a recent recognition. In freshwater ecosystems, detritus or dead organic matter (217) has two possible sources: autochthonous detritus generated within the ecosystem and allochthonous detritus generated externally. This review is concerned with the breakdown of vascular plant detritus whether autochthonous, from aquatic vascular plants, or allochthonous, derived from riparian trees and herbs. The importance to the energetics of streams of vascular plant material from riparian vegetation was recognized in early studies by Nelson & Scott (184), Egglishaw (85), and Minshall (175). Organic matter budgets for various streams have provided quantitative data to support these early observations (96, 132, 182, 254). However, many low-order streams that lack canopies of riparian vegetation may be dominated by autochthonous primary production of nonvascular plant origin. (72, 176). Theoretical models (256) predict increasing importance of autochthonous production by periphyton and aquatic vascular plants for middle-order streams but less importance of these sources in very large streams, mainly due to light limitation. The relative dominance of allochthonous vs autochthonous sources has been shown to vary between stream systems and with local conditions within streams (72, 178). While vascular plant leaves have received most attention in stream research, there is growing recognition that wood is also important. The direct contribution of wood to stream energy budgets is minimal because wood is resistant to breakdown (e.g. 8, 251). However, woody debris is indirectly important because it creates habitat for aquatic organisms (5), promotes

Vascular plant breakdown in freshwater ecosystems

B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

Dioxygen activation by enzymes containing binuclear non-heme iron clusters

Insect digestive enzymes: properties, compartmentalization and function

/pdf/an-introduction-to-the-aquatic-insects-of-north-america-20i7stzjkw.pdf

An Introduction to the Aquatic Insects of North America

Plasmid pRO1957, which contains a 26.5-kb fragment from the chromosome of Pseudomonas pickettii PKO1, allows P. aeruginosa PAO1 to grow on toluene or benzene as a sole carbon and energy source. A subclone of pRO1957, designated pRO1966, when present in P. aeruginosa PAO1 grown in lactate-toluene medium, accumulates m-cresol in the medium, indicating that m-cresol is an intermediate of toluene catabolism. Moreover, incubation of such cells in the presence of 18O2 followed by gas chromatography-mass spectrometry analysis of m-cresol extracts showed that the oxygen in m-cresol was derived from molecular oxygen. Accordingly, this suggests that toluene-3-monooxygenation is the first step in the degradative pathway. Toluene-3-monooxygenase activity is positively regulated from a locus designated tbuT. Induction of the toluene-3-monooxygenase is mediated by either toluene, benzene, ethylbenzene, or m-cresol. Moreover, toluene-3-monooxygenase activity induced by these effectors also metabolizes benzene and ethylbenzene to phenol and 3-ethylphenol, respectively, and also after induction, o-xylene, m-xylene, and p-xylene are metabolized to 3,4-dimethylphenol, 2,4-dimethylphenol, and 2,5-dimethylphenol, respectively, although the xylene substrates are not effectors. Styrene and phenylacetylene are transformed into more polar products.

A novel toluene-3-monooxygenase pathway cloned from Pseudomonas pickettii PKO1.

We studied the degradation of toluene for bacteria isolated from hypoxic (i.e., oxygen-limited) petroleum-contaminated aquifers and compared such strains with other toluene degraders. Three Pseudomonas isolates, P. pickettii PKO1, Pseudomonas sp. strain W31, and P. fluorescens CFS215, grew on toluene when nitrate was present as an alternate electron acceptor in hypoxic environments. We examined kinetic parameters (K(m) and Vmax) for catechol 2,3-dioxygenase (C230), a key shared enzyme of the toluene-degradative pathway for these strains, and compared these parameters with those for the analogous enzymes from archetypal toluene-degrading pseudomonads which did not show enhanced, nitrate-dependent toluene degradation. C230 purified from strains W31, PKO1, and CFS215 had a significantly greater affinity for oxygen as well as a significantly greater rate of substrate turnover than found for the analogous enzymes from the TOL plasmid (pWW0) of Pseudomonas putida PaW1, from Pseudomonas cepacia G4, or from P. putida F1. Analysis of the nucleotide and deduced amino acid sequences of C23O from strain PKO1 suggests that this extradiol dioxygenase belongs to a new cluster within the subfamily of C23Os that preferentially cleave monocyclic substrates. Moreover, deletion analysis of the nucleotide sequence upstream of the translational start of the meta-pathway operon that contains tbuE, the gene that encodes the C230 of strain PKO1, allowed identification of sequences critical for regulated expression of tbuE, including a sequence homologous to the ANR-binding site of Pseudomonas aeruginosa PAO. When present in cis, this site enhanced expression of tbuE under oxygen-limited conditions. Taken together, these results suggest the occurrence of a novel group of microorganisms capable of oxygen-requiring but nitrate-enhanced degradation of benzene, toluene, ethylbenzene, and xylenes in hypoxic environments. Strain PKO1, which exemplifies this novel group of microorganisms, compensates for a low-oxygen environment by the development of an oxygen-requiring enzyme with kinetic parameters favorable to function in hypoxic environments, as well as by elevating synthesis of such an enzyme in response to oxygen limitation.

Catechol 2,3-dioxygenases functional in oxygen-limited (hypoxic) environments.

Larvae of the woodwasp, Sirex cyaneus, contain midgut digestive enzymes that enable them to utilize the major fungal and plant polysaccharides found in their food. At least two classes of enzymes, the C(chi)-cellulases and the xylanases, are not produced by the larvae. Instead, larvae acquire these enzymes while ingesting tissue of Amylostereum chailletii, the fungal symbiont that occurs in the wood on which the larvae feed.

https://science.sciencemag.org/content/sci/220/4602/1161.full.pdf

Acquisition of Digestive Enzymes by Siricid Woodwasps from Their Fungal Symbiont

The digestive system of larvae of Tipula abdominalis (Diptera, Tipulidae), a stream detritivore, is poorly adapted for the digestion of the major polysaccharides in its diet, but well adapted for the digestion of protein. These crane fly larvae are unable to digest the major cell wall polysaccharides of higher plants, i.e., cellulose, hemicellulose and pectin. The only polysaccharides toward which the midguts of T. abdominalis exhibited any activity were α-amylose and laminarin, indicating that polysaccharide digestion is restricted to α-1,4-and β-1,3-glucans. The most concentrated source of these two classes of carbohydrates in submerged leaf litter would be associated fungal tissue. The midgut of T. abdominalis is strongly alkaline throughout, with a maximum pH near 11.5 in a narrow zone near the midpoint. Proteolytic activity in the midgut is extraordinarily high, and the pH optimum for midgut proteolytic activity is above 11. We conclude that the high alkalinity and high proteolytic activity observed in T. abdominalis larvae are manifestations of a highly efficient protein-digesting system, a system of crucial importance to a nitrogen-limited organism which must derive its nitrogen from a resource in which much of the limited nitrogen present is in a "bound" form in complexes of proteins with lignins and polyphenols.

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/47733/442_2004_Article_BF00346265.pdf;sequence=1

Jerome J. Kukor

Papers

A novel toluene-3-monooxygenase pathway cloned from Pseudomonas pickettii PKO1.

Catechol 2,3-dioxygenases functional in oxygen-limited (hypoxic) environments.

Acquisition of Digestive Enzymes by Siricid Woodwasps from Their Fungal Symbiont

The digestion of protein and carbohydrate by the stream detritivore, Tipula abdominalis (Diptera, Tipulidae)

Sequence analysis of the gene cluster encoding toluene-3-monooxygenase from Pseudomonas pickettii PKO1