The Zymomonas mobilis gene encoding acid phosphatase, phoC, has been cloned and sequenced. The gene spans 792 base pairs and encodes an Mr 28,988 polypeptide. This protein was identified as the principal acid phosphatase activity in Z. mobilis by using zymograms and was more active with magnesium ions than with zinc ions. Its promoter region was similar to the -35 "pho box" region of the Escherichia coli pho genes as well as the regulatory sequences for Saccharomyces cerevisiae acid phosphatase (PHO5). A comparison of the gene structure of phoC with that of highly expressed Z. mobilis genes revealed that promoters for all genes were similar in degree of conservation of spacing and identity with the proposed Z. mobilis consensus sequence in the -10 region. The phoC gene contained a 5' transcribed terminus which was AT rich, a weak ribosome-binding site, and less biased codon usage than the highly expressed Z. mobilis genes.

Glycerol-derived membrane lipids are essentially absent in the thermophilic bacterium Thermomicrobium roseum. A series of straight chain and internally methyl-branched 1,2-diols of carbon numbers C(18) to C(23) were found to replace glycerolipids in this bacterium. Fatty acids were present but were ester-linked to the diols or amide-linked to polar heads groups and not to glycerol. This thermophile has evolved the integration of diols as a novel approach for the construction of its cytoplasmic membrane.

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Long-chain 1,2-diols constitute the hydrophobic backbone of membrane lipids (replacing glycerolipids) in the thermophilic eubacterium Thermomkrobium roseum. The effects of incubation temperature on chain length and chain branching of diols and fatty acids were investigated. The maintenance of appropriate membrane fluidity is of particular interest in thermophilic bacteria, as membrane stability has been suggested as a major factor in the ability of microorganisms to live in very hot environments (4, 13).Thermomicrobium roseum is an extremely thermophilic, gram-negative eubacterium (optimal growth temperature of about 70°C) (8). It has an atypical cell wall lacking any significant amount of peptidoglycan (15). The membrane lipids of this unusual organism were investigated, and a series of straight-chain and methyl-branched long-chain 1,2-diols was found (18). The diol-based lipids of T. roseum replace the usual glycerol-based lipids and can be considered the structural equivalent of a glycerol molecule plus one fatty acyl, aldehyde, or alcohol side chain: CH2-R CH-OH CH2-OHStraight-chain and methyl-branched fatty acids were also shown to be present in the membrane lipids of T. roseum (18). With the fatty acid ester-linked to the diol (or possibly, amide linked via a polar head group), the acylated diol could provide the double-chain form typical of glycerol-based lipids.In the present study we undertook to investigate the effect of growth temperature on the diols and fatty acids of T. roseum. T. roseum ATCC 27502 was grown in liquid medium * Corresponding author. 655 (American Type Culture Collection) at pH 8.5. Growth curves were determined in triplicate for each temperature (60, 65, 70, and 75°C), and cells for lipid analysis were harvested from one 2-liter batch in the late log phase. Total lipids were extracted from the wet cell pellet (after centrifugation to recover cells) by a modification of the method of Bligh and Dyer (3).The diols and fatty acids were recovered from acid methanolysis of the total lipids as described previously (10,18). The fatty acid ester distribution was determined by gas chromatography (18) against standards. Diols were analyzed as their alkane derivatives (10) and identified by gas chromatography (18) against alkane standards and against known mixtures of diols converted to alkanes. Diols were 'also analyzed as their acetate derivatives (9).The effect of increased temperature on the distribution of diols and of fatty acids is shown in Tables 1 and 2. The results indicate that T. roseum responds to increased temperatures primarily by decreasing the ratio of branched to straight chains, although there is also a small increase in average chain length with temperature (Table 3).The internal methyl branching on both diols and fatty acids is somewhat unusual, although 10-methylstearic acid

At the heart of debates among creationists and evolutionists are questions about scientific integrity and rigor. Creationists often justify their rejection of biological evolution by claiming that the methodologies and interpretations of evolutionary scientists are flawed. A consideration of creationists' critiques of the scientific data, however, reveals a deficient understanding and appreciation of the nature of the scientific process. It is essential that our schools educate students about the character of scientific inquiry. Clarifying the nature and limitation of scientific knowledge for our students will equip our students to evaluate evolutionary or creationist arguments critically. Recognizing and teaching both the strengths and limitations of the scientific process will do much to further the ongoing dialogue between science and religion.