Comamonas acidovorans strain MC1: a new isolate capable of degrading the chiral herbicides dichlorprop and mecoprop and the herbicides 2,4-D and MCPA

A gram-negative prototrophic bacterial species, strain MC1, was isolated from the vicinity of herbicide-contaminated building rubble and identified by 16S rDNA sequence analysis, its physiological properties, GC content, and fatty acid composition as Comamonas acidovorans. This strain displays activity for the productive degradation of the two enantiomers of dichlorprop [(RS)-2-(2,4-dichlorophenoxy-)propionate; (RS)-2,4-DP] and mecoprop [(RS)-2-(4-chloro-2-methyl-) phenoxypropionate; (RS)-MCPP] in addition phenoxyacetate herbicides, i.e. 2,4-dichlorophenoxyacetate (2,4-D) and 4-chloro-2-methylphenoxyacetate (MCPA), and various chlorophenols were utilized. Rates amounted to 1.2 mmoles/h g dry mass (2,4-D) and 2.7 mmoles/h g dry mass [(RS)-2,4-DP]. Degradation of (RS)-2,4-DP was not inhibited up to concentrations of 500 mg/l, nor of 2,4-D up to 200 mg/l. The optimum pH value of (RS)-2,4-DP degradation was around 8. The application of respective primers for PCR amplification revealed the presence of tfdB and tfdC genes.

Adaptive responses of Ralstonia eutropha to feast and famine conditions analysed by flow cytometry

Results obtained by flow cytometry allow conclusions to be drawn about how the physiological states of Ralstsonia eutropha JMP134 are connected with survival strategies under distinct growth conditions. During both feast and famine conditions the cells were found to proceed through sharply separated phases of life. Two sources of carbon and energy, one poor (0.02% phenol) and one rich (0.2% pyruvate and 0.1% yeast extract) were chosen to study the cellular responses. Despite the major differences in carbon source, when growth stages of the bacteria on the two substrates were characterised in batch growth, only minor differences were found in the time course of the membrane potential related fluorescence intensity (MPRFI). This also applied to the rRNA content and the size-correlated forward scatter (FSC) signal of the cells, both of which increased to high levels during the (early) exponential growth phase. On the rich medium, DNA synthesis initially occurred in an uncoupled manner, then a high rate of PHB formation followed when nutrients began to be limiting. Under famine conditions, the cellular responses were much more complex. PHB was synthesised, then DNA synthesis occurred in a 'eukaryotic' mode, to be succeeded by renewed PHB synthesis. To obtain defined cell physiological states, the chemostat technique was used in addition to batch experiments. The results obtained clearly indicated that key events in cell physiology, including initiation of DNA replication and overflow metabolism, occurred in a hierarchically ordered manner and were tightly correlated with changes in the environmental conditions of the bacterial cells.

Oral administration of (14)C labeled gelatin hydrolysate leads to an accumulation of radioactivity in cartilage of mice (C57/BL)

Several investigations showed a positive influence of orally administered gelatin on degenerative diseases of the musculo-skeletal system. Both the therapeutic mechanism and the absorption dynamics, however, remain unclear. Therefore, this study investigated the time course of gelatin hydrolysate absorption and its subsequent distribution in various tissues in mice (C57/BL). Absorption of (14)C labeled gelatin hydrolysate was compared to control mice administered (14)C labeled proline following intragastric application. Plasma and tissue radioactivity was measured over 192 h. Additional "gut sac" experiments were conducted to quantify the MW distribution of the absorbed gelatin using SDS-electrophoresis and HPLC. Ninety-five percent of enterally applied gelatin hydrolysate was absorbed within the first 12 h. The distribution of the labeled gelatin in the various tissues was similar to that of labeled proline with the exception of cartilage, where a pronounced and long-lasting accumulation of gelatin hydrolysate was observed. In cartilage, measured radioactivity was more than twice as high following gelatin administration compared to the control group. The absorption of gelatin hydrolysate in its high molecular form, with peptides of 2.5-15kD, was detected following intestinal passage. These results demonstrate intestinal absorption and cartilage tissue accumulation of gelatin hydrolysate and suggest a potential mechanism for previously observed clinical benefits of orally administered gelatin.

Induction of heat shock proteins in response to primary alcohols in Acinetobacter calcoaceticus

Cells of Acinetobacter calcoaceticus 69-V, a species able to metabolize a range of aliphatic hydrocarbons and alcohols, were confronted with ethanol, butanol, hexanol or heat shock during growth on acetate as sole source of carbon and energy. The primary alcohols and the heat shock led to the synthesis of new proteins or amplified expression of specific, common and general proteins, which were detected by silver staining after two-dimensional gel electrophoresis. Some of the alcohol-inducible proteins were identified as heat shock proteins by comparing protein patterns of alcohol-shocked cells with those of heat-shocked cells, and by N-terminal amino acid sequencing. DnaK was found to be amplified after all treatments, but GroEI only after heat shock and ethanol treatment. The N-terminal amino acid sequence of the protein, which was considerably amplified after alcohol treatment and heat shock, shows homology to HtpG (high temperature protein G). Some of the heat shock proteins induced by ethanol differ from those induced by butanol and hexanol, suggesting there are at least two different signals for the induction of some heat shock proteins by primary alcohols. This could be due to the different localization of ethanol, butanol and hexanol in the membrane, or because higher cytoplasmic concentrations of ethanol than of butanol or hexanol were applied in these tests in order to keep concentrations of the alcohols in the membrane roughly similar. Besides heat shock proteins, a group of proteins were observed which were only induced by butanol and hexanol, possibly indicating the existence of a further defense mechanism against high concentrations of hydrophobic substrates preventing protein denaturation and membrane damage.

Regulation of poly(beta-hydroxybutyrate) synthesis in Methylobacterium rhodesianum MB 126 growing on methanol or fructose

The intracellular concentration of CoA metabolites and nucleotides was determined in batch cultures of Methylobacterium rhodesianum grown on methanol and shifted to growth on fructose. The intracellular concentration of CoA decreased from a high value of 0.6 nmol/mg poly(beta-hydroxybutyrate)-free bacterial dry mass during growth on methanol to a low value of 0.03 nmol/mg poly(beta-hydroxybutyrate)-free bacterial dry mass after a shift to fructose as a carbon source. The levels of NADH, NADPH, and acetyl-CoA were also lower. Under these conditions, acetyl-CoA was metabolized by both citrate synthase and beta-ketothiolase, and poly(beta-hydroxybutyrate) synthesis and growth occurred simultaneously during growth on fructose. Moreover, the level of ATP was approximately 50% lower during growth on fructose, supporting the hypothesis of a bottleneck in the energy supply during the growth of M. rhodesianum with fructose.

The toxicity of substituted phenolic compounds to a detoxifying and an acetic acid bacterium

In the detoxifying bacterium Acinetobacter calcoaceticus 69-V and in the acetic acid bacterium Acetobacter methanolicus MB 58, glucose and xylose are oxidized, respectively, via PQQ-dependent membrane-bound dehydrogenases, which are linked to the respiratory chain in a manner enabling energy conservation via electron transport phosphorylation (ETP) in the cytoplasmic membrane. Neither the glucose and gluconic acid nor the xylose and xylonic acid are metabolized. Therefore, measurements of sugar oxidation-driven ATP syntheses ought not to be disturbed by ATP drainage caused by anabolic processes. Studying the effect of substituted phenolic compounds on these energization processes reveals that their toxicity increases with an increasing degree of chlorination and that A. calcoaceticus 69-V is more stable than A. methanolicus MB 58 against chlorinated phenols. On the other hand, A. methanolicus MB 58 is more stable against 2,4-dinitrophenol (2,4-DNP) and 2,4-dichlorophenoxyacetic acid (2,4-D), especially in the acidic pH range, in which the sensitivity of ATP synthesis to the uncouplers is higher than that of respiration. The toxicity caused by protonophoric activities ought to be barely detectable by respiratory and dehydrogenase tests. The luminescence system of Photobacterium phosphoreum tested in the luminescent bacteria test was much more sensitive. This test system should be used as a screening tool and the effects measured must be confirmed by toxicity tests evaluating the stability of bacteria themselves involved in processes of detoxification as well as the production of toxic metabolites, monitored with respect to their velocity and efficiency.

Chemicals and heat generate different protein patterns in Acinetobacter calcoaceticus

The effect of exposing Acinetobacter calcoaceticus 69-V to DNP-stress and heat shock was examined by two-dimensional gel electrophoresis of proteins, which were detected either by autoradiography or by silver staining. Both DNP stress and heat shock led to altered patterns of protein synthesis or concentration. About 10% of the proteins which were synthesized newly or at an increased rate and about 25% of those which were found newly or with an increased concentration after DNP treatment were identified after heat shock, too.

Analysis of the PHA granule-associated proteins GA20 and GA11 in Methylobacterium extorquens and Methylobacterium rhodesianum

Electrophoretic analysis of the proteins bound to poly(3-hydroxybutyric acid), PHB-, granules in Methylobacterium extorquens, M. rhodesianum as well as the PHB-leaky mutants Mu 1 and Mu 11, which were isolated from the latter, resulted in two dominant low-molecular weight proteins, which were referred to as GA11 and GA20. After purification of these proteins antibodies against the GA11 and GA20 protein of M. extorquens were obtained. Both proteins bound to the surface of PHB granules as revealed by immunoelectron microscopy of whole cells of M. extorquens and M. rhodesianum. With cells of the PHB-leaky mutants Mu 1 and Mu 11 no specific labeling was observed. The N-terminal amino acid sequences of the GA11 and the GA20 protein were determined. We found significant homologies between the sequences of the investigated strains. The use of oligonucleotide probes based on the N-terminal sequences of the GA20 protein from M. rhodesianum to identify the corresponding structural genes in various genomic libraries failed.

Competition between beta-ketothiolase and citrate synthase during poly(beta-hydroxybutyrate) synthesis in Methylobacterium rhodesianum

The enzymes beta-ketothiolase and citrate synthase from the facultatively methylotrophic Methylobacterium rhodesianum MB 126, which uses the serine pathway, were purified and characterized. The beta-ketothiolase had a relatively high Km for acetyl-CoA (0.5 mM) and was strongly inhibited by CoA (Ki 0.02 mM). The citrate synthase had a much higher affinity for acetyl-CoA (Km 0.07 mM) and was significantly inhibited by NADH (Ki 0.15 mM). The intracellular concentration of CoA metabolites and nucleotides was determined in M. rhodesianum MB 126 during growth on methanol. The level of CoA decreased from about 0.6 nmol (mg dry mass)-1 during growth to the detection limit when poly(beta-hydroxybutyrate) (PHB) accumulated. Nearly unchanged intracellular concentrations of NADH, NADPH, and acetyl-CoA of about 0.5, 0.6-0.7, and 1.0 nmol (mg dry mass)-1, respectively, were determined during growth and PHB synthesis. During growth, the beta-ketothiolase was almost completely inhibited by CoA, and acetyl-CoA was principally consumed by the citrate synthase. During PHB accumulation, the beta-ketothiolase had about 75% of its maximum activity and showed much higher activity than citrate synthase, which at the actual NADH concentration was about 75% inhibited. NADPH concentration was sufficiently high to allow the unlimited activity of acetoacetyl-CoA reductase (Km NADPH 18 microM). PHB synthesis is probably mainly controlled by the CoA concentration in M. rhodesianum MB 126.

Simultaneous utilization of pyridine and fructose by Rhodococcus opacus UFZ B 408 without an external nitrogen source

A bacterium classified as Rhodococcus opacus, which is able to use pyridine (a potentially growth-inhibiting substrate) as its sole source of carbon, energy and nitrogen, was isolated. In a carbon-limited chemostat culture, the kinetics was determined for growth on both pyridine and a mixture of pyridine and fructose (9 mM/22.15 mM). With growth on pyridine, stable steady states were achieved up to dilution rates of about 0.1 h-1. A further increase in the dilution rate resulted in the progressive accumulation of pyridine in the culture liquid and the cells were washed out. The maximum specific growth rate (mu max = 0.23 h-1) and the Ks value (0.22 mM) for growth on pyridine were determined from the residual pyridine concentrations measured within the range of stable steady states. With growth on the substrate mixture, the specific pyridine consumption rates and the residual pyridine concentrations were lower at similar dilution rates than with growth on pyridine alone, and stable steady states were established at dilution rates of up to 0.13 h-1. The maximum pyridine degradation rate was enhanced to 270 mg pyridine l-1 h-1 compared to 210 mg pyridine l-1 h-1 with growth on pyridine as a single substrate. An external nitrogen source did not need to be added in the case of growth on the substrate mixture. Fructose was assimilated by means of ammonium released from pyridine. Analysis of the nitrogen balance furnished proof that pyridine is an energy-deficient substrate; pyridine was assimilated and dissimilated at a ratio of 1 mol/0.67 mol respectively. The resulting yield coefficient was about 0.55 g dry weight/g pyridine. Moreover, it was demonstrated that, in regard to the biologically usable energy, 1 mol pyridine corresponds to 0.43 mol fructose.

Measurement of Growth at Very Low Rates ((mu) >= 0), an Approach To Study the Energy Requirement for the Survival of Alcaligenes eutrophus JMP 134

Alcaligenes eutrophus JMP 134 was grown in a recycling-mode fermenter with 100% biomass retention on 2,4-dichlorophenoxyacetic acid (2,4-D), phenol, and fructose. The growth pattern obtained given a constant supply of substrates exhibited three phases of linear growth on all three substrates. The transition from phase 1 to phase 2, considered to correspond to the onset of stringent (growth) control as indicated by a significant increase in guanosine 5(prm1)-bisphosphate 3(prm1)-bisphosphate (ppGpp), took place at 0.016 h(sup-1) with 2,4-D and at about 0.02 h(sup-1) with phenol and fructose. In the final phase, phase 4, which was achieved after the growth rate on the respective substrates fell below 0.003 to 0.001 h(sup-1), a constant level of biomass was obtained irrespective of further feeding of substrate at the same rate. The yield coefficients decreased by 70 to 80% from phase 1 to phase 3 and were 0 in phase 4. The stationary substrate concentrations s(infmin) in phase 4, calculated from the kinetic constants of the strain, were 1.23, 0.34, and 0.23 (mu)M for 2,4-D, phenol, and fructose, respectively. These figures characterize the minimum stationary substrate concentrations required in a dynamic system to keep A. eutrophus alive. This is caused by a substrate flux which enables growth at a rate >=0 due to the provision of energy to an extent at least satisfying maintenance requirements. According to the constant feed rates of the substrates and the final and stable biomass concentrations, this maintenance energy amounts to 14.4, 4.0, and 2.4 (mu)mol of ATP (middot) mg of dry mass(sup-1) h(sup-1) for 2,4-D, phenol, and fructose, respectively, after correction for the fraction of living cells. The increased energy expenditure in the case of 2,4-D is discussed with respect to uncoupling.

Isolation and purification of granule-associated proteins relevant for poly(3-hydroxybutyric acid) biosynthesis from methylotrophic bacteria relying on the serine pathway

The poly(3-hydroxybutyric acid) (PHB) granules from eight methylotrophic bacteria that use the serine pathway were isolated in a sucrose gradient (1–2 M); these bacteria included members of the genus Methylobacterium, Mycoplana rubra, and PHB-leaky mutants of Methylobacterium rhodesianum. As shown by sodium dodecyl sulfate – polyacrylamide gel electrophoresis, the granules from all investigated methylotrophic strains revealed two major bands representing small proteins. An efficient purification procedure for these two low molecular weight proteins associated with the PHB granules was developed by solubilization of the proteins with Triton X-114 and affinity chromatography on Procion Blue-H-ERD.Key words: poly(3-hydroxybutyric acid), granule-associated proteins, methylotrophic bacteria.

Considerations on the structure and biochemistry of bacterial polyhydroxyalkanoic acid inclusions

Some mathematical calculations were done that provided information about the structure and biochemistry of polyhydroxyalkanoic acid (PHA) granules and about the amounts of the different constituents that contribute to the PHA granules. The data obtained from these calculations are compared with data from the literature, which show that PHA granules consist not only of the polyester but also of phospholipids and proteins. The latter are referred to as granule-associated proteins, and they are always located at the surface of the PHA granules. A concept is proposed that distinguishes four classes of structurally and functionally different granule-associated proteins: (i) class I comprises the PHA synthases, which catalyze the formation of ester linkages between the constituents; (ii) class II comprises the PHA depolymerases, which are responsible for the intracellular degradation of PHA, (iii) class III comprises a new type of protein, which is referred to as phasins and which has most probably a function analogous to that of oleosins in oilseed plants, and (iv) class IV comprises all other proteins, which have been found to be associated with the granules but do not belong to classes I-III. Particular emphasis is placed on the phasins, which constitute a significant fraction of the total cellular protein. Phasins are assumed to form a close protein layer at the surface of the granules, providing the interface between the hydrophilic cytoplasm and the much more hydrophobic core of the PHA inclusion.

Degradation of refinery products and oils from polluted sites by the autochthonous microorganisms of contaminated and pristine soils

The degradation of five refinery products with different boiling ranges and four mineral oils extracted from long-term contaminated soils was monitored by measuring oxygen consumption and the concentration of the total hydrocarbons. Degradation was catalyzed by the isolated communities of the microorganisms from contaminated and pristine soils in an aqueous medium, and partly also directly in the soils. Degradation exceeding 95% was achieved for diesel fuel and spindle oil. The higher-boiling raffinates and the extracts of long-term contaminated soils were degraded by 40-60%. The extracted oils have higher boiling ranges and are therefore more difficult to degrade. Moreover, the progressive enrichment of persistent (including lower-boiling) hydrocarbons decreases the degree of degradation attainable of such aged oils. Whereas in the medium term the autochthonous microorganisms of the contaminated soils showed better degradation efficiency, in the long term the populations of the natural soils caught up with them. This may be due to a sociological adaptation process.

The glucose dehydrogenase-mediated energization of Acinetobacter calcoaceticus as a tool for evaluating its susceptibility to, and defence against, hazardous chemicals

Cells of Acinetobacter calcoaceticus 69-V could be energized by glucose oxidation after the growth on acetate, ethanol, hexanol and benzoate. The velocities of glucose oxidation-driven ATP syntheses were relatively constant in the range from pH 5.4 to 7.5. With decreasing pH values (7.0, 6.0, 5.4) ATP synthesis was inhibited more strongly by the action of 2,4-dinitrophenol and at the same pH value glucose oxidation was nearly unimpaired or inhibited more weakly. This finding is expressed by a decrease of the P/O ratios, indicating the uncoupling of the electron-transport phosphorylation by 2,4-dinitrophenol. The sensitivity towards this uncoupling effect was higher in ethanol-grown cells of Acinetobacter calcoaceticus 69-V than in hexanol- or acetate-grown cells. This increase in sensitivity was accompanied by a decrease of the ratio of saturated (mainly C16:0) to unsaturated (C16:1, C18:1) fatty acids in ethanol-grown cells compared with hexanol-grown ones. The knowledge of such differences in the susceptibility and its molecular background, e.g. possible substrate-induced changes of the fatty acid composition of the cytoplasmic membranes, should help elucidate mechanisms of poisoning by membrane-active hazardous chemicals and develop defence strategies.

Classification of oxygen transport to tissue with neural networks

In the current stage of the development of the EMPHO II it was shown that the transport of oxygen to tissue can be classified for all applications in real time by using neural networks. The resolution of the oxygen classification is 1%. The implementation of the neural network is possible on a commercial signal processor TMS 320C30 board which is compatible with an IBM PC. The implementation of the neural network is done fully in software and no special neurocomputer is necessary. The results are very promising so that the neural network design goals will be established in the future. In the future further efforts will be made in order to increase the data base and to train the network in more detail.

The growth rate-limiting reaction in methanol-assimilating yeasts

The maximum growth rate of methylotrophic yeasts during growth on methanol is about 0.2 h-1. Since they are able to grow faster on substrates such as glucose we tried to identify the putative limiting step in methanol metabolism within the assimilatory pathway, leading to the formation of a major precursor for biosyntheses, or within the linear dissimilatory sequence. Growth experiments with mixed substrates and determination of some kinetic parameters allowed us to restrict the number of possible pacemaker enzymes. The dissimilatory sequence does not seem to be growth-rate limiting. This also applies to transketolase, transaldolase and fructose-1,6-bisphosphatase. Surprisingly, methanol oxidase appears to be the prime candidate.

The mixed substrate concept, applied for microbial syntheses of metabolites

Microbial overproduction of metabolites is a response to suboptimal conditions for growth and multiplication. It is an energy-wasting process in terms of life insofar as a part of energy of the carbon source remains in the metabolite. From an energetic point of view microbial overproduction can be divided into two categories: i) energy-consuming, ii) energy-yielding. The amount of energy required or made available is considered to be responsible for discrepancies between carbon metabolism-determined possible and experimentally obtained yields. Since the expenditure of energy must be provided by oxidation of carbon source more substrate is consumed than required according to the metabolic pathway. In the case of energy-yielding synthesis energy must be discharged. Various possibilities exist. Since metabolic sequences not involved in the synthesis of the proper product are not switched off completely other synthetic processes and even growth can occur. The energy is thus discharged at the expense of substrate. To increase the experimental yield the energy produced or consumed has to be maintained low. This can be achieved by means of substrate mixtures. The synthesis of by-products and growth are difficult to prevent completely. However, growth can be quite desirable since the catalyst is renewed thus making the product synthesis possible.

[Preparation of preoral sustained-release preparations with a base of biodegradable polymers. 3. Preparation of matrix tablets with a base of poly-3-hydroxybutyric acid]

Poly-3-hydroxybutyric acid belongs to the biological polymers, which are produced by bacterials. The determination of the grain size, moisture content, flowability and the parameters for the direct compression was performed in regard of their use as auxillary substance for the preparation of solid sustained release dosage forms. The production of the matrix tablets was performed on the basis of a factorial design. The content of substance, an addition of Heweten 12 and the compression power served as factors. Caffeine was used as model drug. The in vitro release values show, that all three factors have an influence of the drug release. Optimized matrix tablets were produced on the basis of this result.

Detoxification of formaldehyde by acetic acid bacteria

Formaldehyde resistance of methylotrophic and non-methylotrophic Acetobacter strains was investigated. A facultatively methylotrophic Acetobacter methanolicus (MB58) gets rid of free formaldehyde by assimilating it. Heterotrophically growing cells tolerate 12 mM free formaldehyde. Non-methylotrophic but methanol oxidizing Acetobacter pasteurianus strains possess the same level of formaldehyde resistance. Formaldehyde resistance can be drastically lowered down to 4 mM by blocking the formate dehydrogenase by means of hypophosphite. Acetobacter spp. Martin 1 and LMG 76.10 are not able to oxidize methanol or formaldehyde via formate to CO2 and possess a significantly lower formaldehyde resistance (4 mM). Hence high formaldehyde resistance of the Acetobacter spp. investigated is based above all on a properly operating linear dissimilatory sequence. The dissimilatory RuMP cycle can hardly help detoxify formaldehyde.

Completion of the amino acid sequence of the alpha 1 chain of human basement membrane collagen (type IV) reveals 21 non-triplet interruptions located within the collagenous domain

The cDNA and protein sequences of the N-terminal half of human basement membrane collagen (type IV) have been determined. Overlapping cDNA clones were constructed by repeated primer extension with synthetic oligonucleotides. They cover 2953 bp, beginning at the 5' end of the corresponding mRNA. At the protein level, the sequence of the cyanogen bromide peptide CB6 adjacent to the 7S domain has been additionally elucidated. The data presented here complete the protein sequence and nearly the entire cDNA sequence of the human alpha 1(IV) chain. The amino-terminal half of the alpha 1(IV) chain contains 8 cysteine residues involved in intramolecular and intermolecular cross-links. The entire triple-helical domain of alpha 1(IV) is interrupted by 21 non-triplet regions.

Emulsifier formation with Acinetobacter: search for an excretion-reduced mutant of Acinetobacter calcoaceticus 69-V

After growth on acetate three groups of Acinetobacter strains could be identified with respect to the excretion of a bioemulsifier. Mutants of A. calcoaceticus 69-V were selected which produced reduced amounts of emulsifier.

[Acetobacter methanolicus--a new organism for genetic studies]

A new bacterial strain is described belonging to Acetobacter methanolicus species. It is of industrial value as a producer of protein and methanol products. The strain is acidophile and this feature comprises a conspicuous technological advantage. The results of bacteriophage and cell interactions are reported. They might be potentially useful for elaboration of the transduction technique for the strain. The collection of mutants was obtained including those utilizing methanol, having auxotrophic markers as well as streptomycin and rifampicin resistances. The transfer of plasmids RSF1010 and R68 to Acetobacter methanolicus from other bacteria has been demonstrated.

Structure of human-basement-membrane (type IV) collagen. Complete amino-acid sequence of a 914-residue-long pepsin fragment from the alpha 1(IV) chain

The complete amino acid sequence of the 914-residue-long pepsin fragment alpha 1 (IV)95 from the alpha 1 chain of human placental basement membrane (type IV) collagen is presented. This sequence contains 12 interruptions of the collagenous triplet sequence Gly-Xaa-Yaa which varied in length from 1 to 11 residues. The distribution of amino acids between the Xaa and Yaa position was similar to that found in interstitial collagens but the extent of proline and lysine hydroxylation differed. Computer comparisons of the alpha 1 (IV)95 sequence with those of the interstitial collagen chains did not reveal any homology, whereas a comparison with the partial sequences of mouse tumor and bovine lens capsule alpha 1 (IV) showed an approximately 85% identity. The unique sequence characteristics of type IV collagen are discussed in relation to its macromolecular structure and to the interstitial collagens.