Galactose catabolism in Caulobacter crescentus

Abstract

Caulobacter crescentus wild-type strain CB13 is unable to utilize galactose as the sole carbon source unless derivatives of cyclic AMP are present. Spontaneous mutants have been isolated which are able to grow on galactose in the absence of exogenous cyclic nucleotides. These mutants and the wild-type strain were used to determine the pathway of galactose catabolism in this organism. It is shown here that C. crescentus catabolizes galactose by the Entner-Doudoroff pathway. Galactose is initially converted to galactonate by galactose dehydrogenase and then 2-keto-3-deoxy-6-phosphogalactonate aldolase catalyzes the hydrolysis of 2keto-3-deoxy-6-phosphogalactonic acid to yield triose phosphate and pyruvate. Two enzymes of galactose catabolism, galactose dehydrogenase and 2-keto-3deoxy-6-phosphogalactonate aldolase, were shown to be inducible and independently regulated. Furthermore, galactose uptake was observed to be regulated independently of the galactose catabolic enzymes.

The caulobacters: ubiquitous unusual bacteria.

“…The highest incubation temperature used for the cultivation of C. crescentus was 420C (172); however, 370C has been more commonly used for studies of thermosensitive traits in both wildtype and mutant strains (137,140,172,(206)(207)(208)(209)218). Growth rate is not increased by incubation at temperatures above 300C (140,172,218), as also reported for C. vibrioides (20), C. bacteroides (218), and an unidentified isolate from a stalactite grotto (175).…”

“…Complex nutrients (12,14,15,80,93,97), glucose (152, 160), amino acids and nonnitrogenous organic acids (218), phosphate (152;dexter, unpublished data), and other ions (82, 152, 218) all seem to have low upper limits allowing uninhibited growth and uniform morphology. In C. crescentus in A. biprosthecum, slowly utilized sugars, such as lactose, can, however, be provided at higher (gravimetric) concentrations than glucose (137,140,152).…”

“…Basal solutions used in defined media for caulobactersa(136,137,140,172,249,251), N. Agabian(1,3,60,61,140,143,145,147), A. Fukuda(73,74,99,101), R. G. Riley and B. J. Kolodziej…”

Modular Engineering of Biomass Degradation Pathways

“…The breakdown of glucose into pyruvate by glycolytic pathways is one of the most conserved natural processes [85]. There are multiple routes through glycolysis, including the Embden-Meyerhof-Parnas (EMP) pathway [86], the Entner-Doudoroff (ED) pathway [87,88], the semi-phosphorylated ED pathway [89], the non-phosphorylated ED pathway [90], and the pentose phosphate pathway (PPP) [91,92].…”

“…Galactose is catabolized by many enteric bacteria through the Leloir pathway [100], or by promiscuous activity of the enzymes of other sugar catabolic pathways such as the Entner-Doudoroff (ED) [88,101], De Ley-Doudoroff [101], or lactose metabolic pathways ( Figure 5) [102].…”