Coaggregation among nonflocculating bacteria isolated from activated sludge - PubMed (original) (raw)

Coaggregation among nonflocculating bacteria isolated from activated sludge

Anushree Malik et al. Appl Environ Microbiol. 2003 Oct.

Abstract

Thirty-two strains of nonflocculating bacteria isolated from sewage-activated sludge were tested by a spectrophotometric assay for their ability to coaggregate with one other in two-membered systems. Among these strains, eight showed significant (74 to 99%) coaggregation with Acinetobacter johnsonii S35 while only four strains coaggregated, to a lesser extent (43 to 65%), with Acinetobacter junii S33. The extent and pattern of coaggregation as well as the aggregate size showed good correlation with cellular characteristics of the coaggregating partners. These strains were identified by sequencing of full-length 16S rRNA genes. A. johnsonii S35 could coaggregate with strains of several genera, such as Oligotropha carboxidovorans, Microbacterium esteraromaticum, and Xanthomonas spp. The role of Acinetobacter isolates as bridging organisms in multigeneric coaggregates is indicated. This investigation revealed the role of much-neglected nonflocculating bacteria in floc formation in activated sludge.

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Figures

FIG. 1.

Flocculation characteristics of the sewage sludge isolates.

FIG. 2.

Comparison of results from the two assays (with and without a centrifugation step) for measurement of aggregation indices of larger coaggregates (110 μm) of A. johnsonii S35 and M. esteraromaticum S29 (A) and smaller coaggregates (50 μm) of A. johnsonii S35 and M. esteraromaticum S51 (B).

FIG. 3.

Scanning electron micrographs of the coaggregates. (A) A. johnsonii S35. (B) A. junii S33. (C) A. johnsonii S35 and O. carboxidovorans S23. (D) A. junii S33 and O. carboxidovorans S23. (E) A. johnsonii S35 and M. esteraromaticum S51. (F) A. junii S33 and M. esteraromaticum S51. (G) A. johnsonii S35 and Xanthomonas sp. strain S53.

FIG. 4.

Time courses of coaggregation of A. johnsonii S35 and A. junii S33 with O. carboxidovorans S23 (A), M. esteraromaticum S51 (B), and Xanthomonas sp. strain S53 (C). Symbols: •, A. johnsonii S35; ♦, A. junii S33; ▪, partner strain; ▴, A. johnsonii S35 and partner strain; ▵, A. junii S33 and partner strain.

FIG. 4.

FIG. 5.

Correlation during coaggregation of A. johnsonii S35 with other nonflocculating bacteria. (A) Cell surface hydrophobicity (percent adsorption to _p_-xylene) and aggregation index. (B) Cell surface hydrophobicity and aggregate size. (C) Aggregation index and aggregate size.

FIG. 5.

FIG. 6.

Phase-contrast micrographs of the coaggregates. (A) A. johnsonii S35 and Xanthomonas sp. strain S53. (B) A. johnsonii S35 and Xanthomonas sp. strain S11. Bar, 50 μm.

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Coaggregation among nonflocculating bacteria isolated from activated sludge - PubMed (original) (raw)