As discussed earlier, the complete genome sequence of Z. mobilis ZM4 has been reported recently [12] following earlier related studies by Korean scien­tists [88-90]. It was found that the genome consists of 2 056416 base pairs forming a circular chromosome with 1998 open reading frames (ORFs) and three ribosomal RNA transcription units. As reported by the authors, “the genome lacks recognizable genes for 6-phosphofructokinase, an essential en­zyme in the Embden-Meyerhof-Parnas pathway, and for two enzymes in the tricarboxylic acid (TCA) pathway, the 2-oxoglutarate complex and malate dehydrogenase. Glucose can be metabolized therefore only by the Entner — Doudoroff pathway”.

Comparison of whole genome microarray data for Z. mobilis ZM1 (ATCC10988) and ZM4 (ATCC 31821) revealed that the 54 ORFs present in ZM4 were absent for ZM1. Four of these ORFs that encode trans­port proteins or permeases, and two that encoded for specific enzymes— NAD(P)H:quinone oxidoreductase and an oxidoreductase related to short — chain alcohol dehydrogenases, were found to be highly expressed in Z. mobilis ZM4. The authors suggested that it is possible these genes relate to the higher specific rates of sugar uptake and ethanol production for ZM4 when compared to ZM1. They also reported that two genes encoding capsular carbohydrate synthesis enzymes were only actively expressed in ZM4 and may contribute to its relatively high resistance to increased osmotic pressure found in high sugar solutions (e. g. in 250-300 g L-1 glucose media).

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