Eco-evolutionary modelling of microbial syntrophy indicates the robustness of cross-feeding over cross-facilitation.

Syntrophic cooperation among prokaryotes is ubiquitous and diverse. It relies on unilateral or mutual aid that may be both catalytic and metabolic in nature. Hypotheses of eukaryotic origins claim that mitochondrial endosymbiosis emerged from mutually beneficial syntrophy of archaeal and bacterial partners. However, there are no other examples of prokaryotic syntrophy leading to endosymbiosis. One potential reason is that when externalized products become public goods, they incite social conflict due to selfish mutants that may undermine any mutualistic interactions. To rigorously evaluate these arguments, here we construct a general mathematical framework of the ecology and evolution of different types of syntrophic partnerships. We do so both in a general microbial and in a eukaryogenetic context. Studying the case where partners cross-feed on each other's self-inhibiting waste, we show that cooperative partnerships will eventually dominate over selfish mutants. By contrast, systems where producers actively secrete enzymes that cross-facilitate their partners' resource consumption are not robust against cheaters over evolutionary time. We conclude that cross-facilitation is unlikely to provide an adequate syntrophic origin for endosymbiosis, but that cross-feeding mutualisms may indeed have played that role.

Investigation of oxacillin-hydrolyzing beta-lactamase in borderline methicillin-resistant clinical isolates of Staphylococcus aureus.

BACKGROUND: Mechanisms of borderline resistance of Staphylococcus aureus to penicillinase-resistant penicillins (PRPs) may include hyperproduction of classical penicillinase and/or production of beta-lactamase hydrolyzing also PRPs. METHODS: beta-Lactamase activity of whole cells and purified enzymes was estimated spectrophotometrically and in isolated cytoplasmic membranes by bioassay with Bacillus subtilis as test strain. RESULTS: Out of 53 clinical isolates of S. aureus, 18 showed oxacillin MIC values from 0.5 to 2 microg/ml, which were reduced by sulbactam and/or clavulanic acid in the case of four isolates producing large quantities of inducible, type A beta-lactamase. Cytoplasmic membranes isolated from these strains showed oxacillin-hydrolyzing activity. One of these strains was grown also in the presence of globomycin, an antibiotic known to interfere with the anchorage of membrane lipoproteins; this treatment eliminated the oxacillin-hydrolyzing activity. CONCLUSIONS: The resistance in these strains was due to a membrane-bound lipoprotein with oxacillin-hydrolyzing activity.

Ocular motor dysfunction in Lesch-Nyhan disease.

Eye movements were assessed in 22 patients with varying degrees of hypoxanthine-guanine phosphoribosyltransferase deficiency. Ocular motility was clinically normal in seven patients with moderate enzyme deficiency but grossly abnormal in 15 patients with severe enzyme deficiency. In patients with severe deficiency, fixation was interrupted by frequent unwanted saccades toward minor visual distractions. Voluntary saccades were associated with an initial head movement and/or eyeblink in all of these patients. When head motion was prevented, voluntary saccades were often delayed and sometimes absent. In contrast, saccade speed, reflexive saccades, and other reflexive eye movements appeared clinically normal. Four patients with severe enzyme deficiency also experienced mild blepharospasm, and two had ocular tics. These disturbances of ocular motility are consistent with dysfunction of the basal ganglia or its connections with ocular motor centers in the prefrontal cortex or midbrain.

N-Alkane uptake and utilisation by Streptomyces strains.

Streptomyces strains isolated from the Kuwait Burgan oil field were defined as S. griseoflavus, S. parvus, and S. plicatus utilised n-hexadecane, n-octadecane (purified fractions of mineral oil), kerosene, and crude oil as sole carbon and energy sources. The strains were incubated with n-alkanes and increase of the fatty acid content with chain length equivalent to the employed n-alkanes was observed. Signal transducing GTP-binding proteins (GBPs) play an important role in n-alkane uptake in streptomycetes. Specific activators of GBPs increased the uptake of hydrocarbons. Using the hydrophobic fluorescent dye diphenylhexatrien (DPH) as a probe, it was found that the microviscosity of the hydrophobic inner region of the cellular membrane is significantly lower in hydrocarbon utilisers than in non-utilisers. This difference probably reflects differences in the fatty acid composition of the strains. When cultures were grown in n-alkane containing media, electron microscopy revealed that the hydrocarbon utilisers showed less-electron dense areas as inclusions in the cytoplasm. Soil samples inoculated with Streptomyces strains eliminated hydrocarbons much faster than those not containing these strains, serving as control. When inorganic medium was supplied with n-hexadecane-1-14C as sole carbon and energy source, radioactive CO2 was detected. Since streptomycetes have not been used until now for oil elimination, though they are known as abundant soil bacteria tolerating extreme conditions, their possible use for bioremediation of hydrocarbon contaminated soils is discussed.

A synthetic gamma-lactone group with beta-lactamase inhibitory and sporulation initiation effects.

Previous studies showed that some lactones have beta-lactamase inhibitory or antibacterial effects, others--like A-factor (a gamma-butyrolactone) and its derivatives--stimulate sporulation in Streptomyces griseus strains. Our experiments were aimed at exploring whether synthetic gamma-lactones had such effects. None of the seven gamma-lactones studied showed antibacterial activity, but two of them inhibited beta-lactamases isolated from various bacteria. These two gamma-lactones did not reduce colony formation of murine bone marrow cells in vitro, indicating that they were not toxic to proliferating mammalian cells. Four gamma-lactones, including the two inhibiting beta-lactamase, stimulated sporulation in the non-sporulating S. griseus bald 7 mutant. Further studies of gamma-lactones as potential inhibitors of beta-lactamase seem to be warranted.

Cognitive functioning in Lesch-Nyhan syndrome: a 4-year follow-up study.

Lesch-Nyhan syndrome (LNS) is a rare disorder of metabolism caused by a defective gene on the X chromosome. It is typically characterized by choreoathetosis, hypertonia, hyperreflexia, and self-mutilation. The present study is a 4-year follow-up investigation of the cognitive status of six subjects with a mean age of 17 years 10 months (range 14 years 9 months to 23 years). The Stanford-Binet Intelligence Scale: IV was used. Each of the four domains assessed by this battery (verbal reasoning, abstract/visual reasoning, quantitative, and short-term memory) was compared with previous findings of the same subjects at their initial test and 2-year follow up; the aim being to gain further insight into the clinical course of LNS over time. The results suggest that while the subjects generally continued to acquire new information and skills over time, their standardized scores declined, indicating that a plateau was reached in their skill levels relative to their peers, as also seen in other developmental disabilities. Deficits were noted in working memory, particularly on tasks that involve considering multiple features simultaneously.

Hydrocarbon uptake by Streptomyces.

Oligocarbophilic Streptomyces strains capable of hydrocarbon uptake and utilization were isolated from the polluted desert of Kuwait and used in this study. Transmission electron-microscopy of hyphae revealed that they become enriched with large less electron dense areas in the cytoplasm, when biomass samples were incubated with alkanes. The Streptomyces isolate could utilize n-hexadecane as sole carbon and energy source and their fatty acid content showed an increase in the fatty acids with chain length equivalent to those of the alkane substrates. Fluorescence measurements of diphenylhexatriene dissolved in the representative alkane, n-hexadecane, showed that the kinetics of hydrocarbon uptake are quite different in hydrocarbon-utilizer compared with non-utilizer Streptomyces strain. Microviscosity of the cellular membrane of the utilizer strain was also different from that of the non-utilizer control strain Streptomyces griseus after incubation in the presence of n-hexadecane. Very likely the hydrocarbon utilizer transported these compounds more efficiently across their membranes and accumulated them as inclusions in the cytoplasm.

Evidence of a role for NAD+-glycohydrolase and ADP-ribosyltransferase in growth and differentiation of Streptomyces griseus NRRL B-2682: inhibition by m-aminophenylboronic acid.

m-Aminophenylboronic acid (APBA) inhibited the germination, growth and sporulation of Streptomyces griseus NRRL B-2682 in an age- and concentration-dependent manner in submerged and solid cultures. When added to cells or cell extracts it irreversibly inhibited NAD+-glycohydrolase and ADP-ribosyltransferase activity. ADP-ribosyltransferase was more sensitive, but inhibition was not complete, even in the presence of 10 mM APBA. The in vivo effects of the inhibitor correlated with its in vitro effect on ADP-ribosylation and on the profile of ADP-ribosylated endogenous proteins. The physiological importance of ADP-ribosyltransferase was supported by the observation that APBA strongly inhibited the growth of a non-sporulating and NAD+- glycohydrolase-negative mutant of the parental strain. The resistance of S. griseus NRRL B-2682 strains able to grow in the presence of APBA was due to permeability factors. A comparison of the ADP-ribosylated protein profiles of S. griseus NRRL B-2682 grown under various conditions showed similarities, but also specific differences. The results suggest that the ADP-ribosyltransferase of S. griseus NRRL B-2682 is an indispensable enzyme for growth and differentiation of the strain. It may regulate the activity of key enzymes or developmental proteins by responding to intra- and extracellular conditions.

Cognitive functioning in Lesch-Nyhan syndrome.

The present study represents the first effort to assess systematically the cognitive functioning of a population of individuals with Lesch-Nyhan syndrome using standardized psychometric instruments. Seven residents from a special hospital setting participated. They ranged in age from 10 years 1 month to 22 years 3 months (mean 13 years 7 months). Using the Stanford-Binet Intelligence Scale: IV, scores in each of the four domains assessed by this battery (Verbal Reasoning, Abstract/Visual Reasoning, Quantitative and Short-Term Memory), as well as the general composite score, ranged from moderately mentally retarded to low average. Areas of weakness included attention, the manipulation of complex visual images, the comprehension of complex or lengthy speech, mathematical ability, and multi-step reasoning.

Modification of glutamine synthetase in Streptomyces griseus by ADP-ribosylation and adenylylation.

Addition of NH4+ to STreptomyces griseus 2682 cells grown in NO3- containing medium resulted in a rapid decline in glutamine synthetase activity due to covalent modification of the enzyme. The NH4+ promoted inactivation of the enzyme was inhibited by the ADP-ribosyltransferase inhibitor 3-methoxybenzamide. In the presence of ADP-ribosyltransferase activity the purified glutamine synthetase was also inhibited by NAD+ in a concentration-dependent manner. ADP-ribosylation of glutamine synthetase was demonstrated in vitro by showing the incorporation of labeled ADP-ribose from [alpha-32P]NAD+ into glutamine synthetase subunits. Beside ADP-ribosylation, adenylylation of glutamine synthetase was also shown in S. griseus since phosphodiesterase I treatment reactivated the enzyme in crude extracts of NH(4+)-shocked cells. Glutamine synthetase was also inhibited and modified by ATP in crude cellular extracts. These results suggest that in S. griseus 2682 ADP-ribosylation of glutamine synthetase could be an alternative modification to adenylylation to regulate glutamine synthetase activity.

Age-dependent changes in transmembrane signalling: identification of G proteins in human lymphocytes and polymorphonuclear leukocytes.

In human neutrophils (PMNLs) we found that in the elderly IP3 formation was significantly decreased compared to that of young subjects. For FMLP receptor binding affinity and number no measurable differences occurred upon ageing, studying both the low or the high affinity receptors. The amount of ADP-ribosylated G proteins, catalysed by pertussis toxin (PT) or cholera toxin (CT), was significantly increased in PMNLs of the elderly. In lymphocytes, the PT-catalysed ADP ribosylation of G proteins was also increased with ageing, while the CT-catalysed ribosylation was decreased. The autoradiogram of [32P]ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40,000 M(r). In contrast, in lymphocytes of the elderly, the major polypeptide was 45,000 M(r). In PMNLs, CT labelled quite strongly the 45,000 M(r) band, mainly in the elderly. When PT was used, no age-related pattern changes could be demonstrated, while differences could be observed between the two types of cells. The use of antiserum P680 (G alpha common) showed no age-related pattern changes, while the intensity of the labelled proteins varies with age and cell type. The antiserum U46 (Go alpha) could identify in lymphocytes of young subjects two polypeptides 68,000 and 41,000 M(r). The prominent polypeptide in lymphocytes of the elderly was the 70,000 M(r) and no other polypeptides could be recognized. In PMNLs of young subjects the U46 and serum identified a range of species. In PMNLs of the elderly all these bands were weakly labelled. The present data indicate changes in the pattern and the quantity of G proteins in lymphocytes and PMNLs of elderly subjects.

Care-load for children and young adults with severe cerebral palsy.

Care-load was analysed for 44 children and young adults (mean age 18.9 years) with severe spastic quadriplegia. All were enrolled in a residential school/hospital and used wheelchairs. The majority were in the moderate to borderline range of mental retardation. They were monitored for 24 hours a day over a seven-day period, and were timed in 10 major activities, including basic care (bathing, toileting, dressing, grooming, feeding), as well as sleep, leisure, education/vocation, counseling/psychosocial therapy, medical/nursing care, transportation, and at home. The findings replicated those of an earlier Swedish study, which suggests that the basic care needs of individuals with severe cerebral palsy may be predictable, regardless of the type of care being provided.

The possible role of ADP-ribosylation in sporulation and streptomycin production by Streptomyces griseus.

Mutants resistant to 3-aminobenzamide, a known inhibitor of ADP-ribosyltransferase, were obtained from Streptomyces griseus IFO 13189, a streptomycin-producing strain. One (strain no. 4), which had significantly reduced ADP-ribosyltransferase activity, was analysed in detail. Mutant 4 displayed a conditional phenotype with respect to cultivation temperature. At 30 degrees C, it exhibited severely reduced ability to produce aerial mycelium (on solid medium) and submerged spores and streptomycin (in liquid culture), but this ability was fully restored at 25 degrees C. The mutant produced A-factor normally, regardless of cultivation temperature, and exhibited normal ability to accumulate ppGpp intracellularly. SDS-PAGE analyses of cellular proteins labelled by [32P]NAD revealed that an ADP-ribosylated protein with a molecular size of 44 kDa, which appeared in sporulating cultures of the parent strain, was missing from the mutant grown at the non-permissive temperature (30 degrees C). Genetic analysis showed that the aba mutation conferring resistance to 3-aminobenzamide was tightly linked to the altered phenotype. Failure to ADP-ribosylate certain cellular protein(s), presumably due to the aba mutation, may be responsible for impaired differentiation in this mutant.

The possible role of ADP ribosylation in physiological regulation of sporulation in Streptomyces griseus.

The role of ADP ribosylation of proteins in the physiological regulation of sporulation in Streptomyces griseus was studied. We report here that both the activity of NAD+: arginine ADP-ribosyltransferase (ADPRT) and the pattern of ADP-ribosylated proteins showed characteristic changes during the life cycle in S. griseus 2682. Analysis off ADP-ribosylated proteins revealed that in a nonsporulating mutant of the parental wild-type (wt) strain (Bld7 mutant), both the activity of ADPRT and the pattern of ADP-ribosylated proteins were different from those of the parental strain. Addition of 3-aminobenzamide (3AB), the most potent inhibitor of ADPRT, inhibited sporulation of S. griseus 2682 and the A-factor (AF)-induced sporulation of S. griseus Bld7, but in both cases the inhibitory effect of 3AB was strictly age-dependent. Using [alpha-32P]GTP, we have demonstrated the presence of GTP-binding proteins in purified cell membranes of S. griseus 2682 and S. griseus Bld7. The same GTP-binding proteins were observed in Bld7 and the wt. AF stimulated the basal GTPase activity of cell membranes of S. griseus 2682 in a concentration-dependent manner, suggesting that GTP-binding proteins might be involved in the AF-induced sporulation process.

Transmembrane signaling changes with aging.

Altered immune response and transmembrane signaling with aging has previously been demonstrated. The aim of the present study was to characterize PMNLs and lymphocyte G proteins and to determine whether their relative amounts are altered with aging. First we studied the effects of FMLP on PMNLs IP3 formation. It was found that in any group of elderly the PMNLs IP3 formation was significantly decreased compared to that of young subjects. In FMLP receptor binding affinity no measurable difference exists in either low- or high-affinity FMLP receptors. The autoradiogram of 32P-ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40 kDa, and two much less prevalent components of 52 and 45 kDa. In contrast, in lymphocytes of elderly subjects the major polypeptide was 45 kDa, and the two others were very weakly labeled. In PMNLs, CT labeled the 45-kDa band quite strongly, mainly in the elderly, and the 52- and 40-kDa bands were very weakly labeled, mainly in young subjects. When PT was used, no age-related pattern changes could be demonstrated, while differences could be observed between the two types of cells.

Combined hamartoma of the retina and retinal pigment epithelium in a patient with neurofibromatosis type 2.

We describe a young patient with combined hamartoma of the retina and retinal pigment epithelium who developed bilateral acoustic neuromas and meningiomas of the cervical-medullary junction and fifth cranial nerve. This case illustrates the association between combined hamartoma of the retina and retinal pigment epithelium and neurofibromatosis type 2. The authors recommend that children with a combined hamartoma of the retina and retinal pigment epithelium be screened for neurofibromatosis type 2.

ADP-ribosylation of membrane proteins of Streptomyces griseus strain 52-1.

Membranes purified from cells of Streptomyces griseus strain 52-1 possess an ADP-ribosyltransferase activity. The enzyme transfers the ADP-ribose moiety of NAD to one major membrane protein of Mr 32,000 and 2-3 minor proteins of larger molecular weights. The effects of inhibitors on the ADP-ribosyltransferase activity proves that the reaction is enzymatic and suggests that the enzyme ADP-ribosylates the guanidine group of arginine. The kinetics of liberation of ADP-ribose during alkaline hydrolysis of the modified proteins is consistent with the arginine-ADP-ribose bond. This is the first report of ADP-ribosylation of proteins in a Gram-positive bacterium.

In vitro investigation of BK-218, a new oral and parenteral cephalosporin.

The antibacterial activity of BK-218 was similar to that of cefamandole when it was tested against several laboratory strains. The inhibiting effect of BK-218 was greater than that of cephalexin and cefoxitin on penicillin-binding proteins of Escherichia coli HB101. This result was in close correlation with the relative inhibition of radiolabeled glucosamine incorporation (greatest with BK-218) and with the lytic effect (most intensive with BK-218). BK-218 proved to be a good inhibitor for all five of the beta-lactamases that were investigated, although two enzymes (Enterobacter cloacae P99 and Pseudomonas aeruginosa Cilote) hydrolyzed it to some extent.

Effect of aminoglycoside antibiotics on the autolytic enzyme of Streptomyces griseus.

The isolated cell wall of Streptomyces griseus 52-1 strain labelled with fluorescein isothiocyanate (FITC) and containing wall-bound autolytic enzyme was lysed as a function of different cations. The autolysis was accelerated by aminoglycoside antibiotics (streptomycin and the structurally closely related neomycin) which have a polycationic character. Since this strain is a streptomycin producer it is suggested that streptomycin may have a regulatory function on autolysis.