Complex Expression of the Cellulolytic Transcriptome of Saccharophagus degradans

Abstract

Saccharophagus degradans is an aerobic marine bacterium that can degrade cellulose by the induced expression of an unusual cellulolytic system composed of multiple endoglucanases and glucosidases. To understand the regulation of the cellulolytic system, transcript levels for the genes predicted to contribute to the cellulolytic system were monitored by quantitative real-time PCR (qRT-PCR) during the transition to growth on cellulose. Four glucanases of the cellulolytic system exhibited basal expression during growth on glucose. All but one of the predicted cellulolytic system genes were induced strongly during growth on Avicel, with three patterns of expression observed. One group showed increased expression (up to 6-fold) within 4 h of the nutritional shift, with the relative expression remaining constant over the next 22 h. A second group of genes was strongly induced between 4 and 10 h after nutritional transfer, with relative expression declining thereafter. The third group of genes was slowly induced and was expressed maximally after 24 h. Cellodextrins and cellobiose, products of the predicted basally expressed endoglucanases, stimulated expression of representative cellulase genes. A model is proposed by which the activity of basally expressed endoglucanases releases cellodextrins from Avicel that are then perceived and transduced to initiate transcription of each of the regulated cellulolytic system genes forming an expression pattern.

Cellulose and hemicellulose decomposition by forest soil bacteria proceeds by the action of structurally variable enzymatic systems

“…Such general induction may be more efficient than a complex regulatory system recognizing various polysaccharides if we consider the variability of these structures. So far, the regulatory systems that respond to the presence of cellulose degradation products such as cellobiose and other cellodextrins remain unknown in most bacteria 35 . However, some studies showed that certain bacteria express glycosyl hydrolases even during growth on glucose 35 36 .…”

“…So far, the regulatory systems that respond to the presence of cellulose degradation products such as cellobiose and other cellodextrins remain unknown in most bacteria 35 . However, some studies showed that certain bacteria express glycosyl hydrolases even during growth on glucose 35 36 . One of these studies showed that glucose induced similar CAZymes as cellulose in Clostridium cellulolyticum and that cellulose was more quickly degraded when glucose was present, hypothesizing that this basal expression may mediate a faster response of the bacteria to cellulose availability 36 .…”

Evaluating bacterial community structures in oil collected from the sea surface and sediment in the northern Gulf of Mexico after the Deepwater Horizon oil spill

“…The excitation-emission matrix (EEM) analysis on the overlying water showed a clear oil-related contour (Ex 270-290 nm, Em 330-360 nm, data not shown), which resembles an oil component (C2) of the crude oil (Zhou et al 2013). Interestingly, Saccharophagus degradans, a cellulose degrader (Zhang and Hutcheson 2011), represented 9% of the bacterial community in the overlying water. One possible explanation for the growth of this bacterium is that oil degraders in sediment produced polysaccharide-related biosurfactants (Desai and Banat 1997), such as rhamnolipids by Pseudomonas.…”

Biochemical characterization of 4-α-glucanotransferase fromSaccharophagus degradans2-40 and its potential role in glycogen degradation

“…cDNA was then used as a template for RT‐PCR with the primer pairs listed in Table S1. Guanylate kinase ( spoR ) was used as a reference gene (Zhang & Hutcheson, ).…”