Lactobacilli are gram-positive bacteria that are a subdominant element in the human gastrointestinal microbiota, and which are commonly used in the food industry. Some lactobacilli are considered probiotic, and have been associated with health benefits. However, there is very little culture-independent information on how consumed probiotic microorganisms might affect the entire intestinal microbiota. We therefore studied the impact of the administration of Lactobacillus salivarius UCC118, a microorganism well characterized for its probiotic properties, on the composition of the intestinal microbiota in two model animals. UCC118 has anti-infective activity due to production of the bacteriocin Abp118, a broad-spectrum class IIb bacteriocin, which we hypothesized could impact the microbiota. Mice and pigs were administered wild-type (WT) L. salivarius UCC118 cells, or a mutant lacking bacteriocin production. The microbiota composition was determined by pyrosequencing of 16S rRNA gene amplicons from faeces. The data show that L. salivarius UCC118 administration had no significant effect on proportions of major phyla comprising the mouse microbiota, whether the strain was producing bacteriocin or not. However, L. salivarius UCC118 WT administration led to a significant decrease in Spirochaetes levels, the third major phylum in the untreated pig microbiota. In both pigs and mice, L. salivarius UCC118 administration had an effect on Firmicutes genus members. This effect was not observed when the mutant strain was administered, and was thus associated with bacteriocin production. Surprisingly, in both models, L. salivarius UCC118 administration and production of Abp118 had an effect on gram-negative microorganisms, even though Abp118 is normally not active in vitro against this group of microorganisms. Thus L. salivarius UCC118 administration has a significant but subtle impact on mouse and pig microbiota, by a mechanism that seems at least partially bacteriocin-dependent.

Bacteriocins produced by Lactobacillus salivarius isolates derived from a gastrointestinal origin have previously demonstrated efficacy for in vivo protection against Listeria monocytogenes infection. In this study, comparative genomic analysis was employed to investigate the intraspecies diversity of seven L. salivarius isolates of human and porcine intestinal origin, based on the genome of the well-characterized bacteriocin-producing strain L. salivarius UCC118. This revealed a highly conserved megaplasmid-borne gene cluster in these strains involved in the regulation and secretion of two-component class IIb bacteriocins. However, considerable intraspecific variation was observed in the structural genes encoding the bacteriocin peptides. They ranged from close relatives of abp118, such as salivaricin P, which differs by 2 amino acids, to completely novel bacteriocins, such as salivaricin T, which is characterized in this study. Salivaricin T inhibits closely related lactobacilli and bears little homology to previously characterized salivaricins. Interestingly, the two peptides responsible for salivaricin T activity, SalTα and SalTβ, share considerable identity with the component peptides of thermophilin 13, a bacteriocin produced by Streptococcus thermophilus. Furthermore, the salivaricin locus of strain DPC6488 also encodes an additional novel one-component class IId anti-listerial bacteriocin, salivaricin L. These findings suggest a high level of redundancy in the bacteriocins that can be produced by intestinal L. salivarius isolates using the same enzymatic production and export machinery. Such diversity may contribute to their ability to dominate and compete within the complex microbiota of the mammalian gut.

Two-component salivaricin P-like bacteriocins have demonstrated potential as antimicrobials capable of controlling infections in the gastrointestinal tract (GIT). The anti-Listeria activity of salivaricin P is optimal when the individual peptides Sln1 and Sln2 are added in succession at a 1:1 ratio. However, as degradation by digestive proteases may compromise the functionality of these peptides within the GIT, we investigated the potential to create salivaricin variants with enhanced resistance to the intestinal protease trypsin. A total of 11 variants of the salivaricin P components, in which conservative modifications at the trypsin-specific cleavage sites were explored in order to protect the peptides from trypsin degradation while maintaining their potent antimicrobial activity, were generated. Analysis of these variants revealed that eight were resistant to trypsin digestion while retaining antimicrobial activity. Combining the complementary trypsin-resistant variants Sln1-5 and Sln2-3 resulted in a MIC(50) of 300 nM against Listeria monocytogenes, a 3.75-fold reduction in activity compared to the level for wild-type salivaricin P. This study demonstrates the potential of engineering bacteriocin variants which are resistant to specific protease action but which retain significant antimicrobial activity.

We investigated the bactericidal activity and exclusion effect of 10 strains of lactic acid bacteria (LAB) isolated from different commercial food products and infant feces against Helicobacter pylori (H. pylori) in human gastric epithelial AGS cells. Antagonistic activity of spent culture supernatants (SCS) from LAB (LAB-SCS) was tested, and the content of organic acids in SCS was analyzed with high-performance liquid chromatography (HPLC). In addition, the bactericidal activities of LAB-SCS were estimated by a time-kill assay and by measuring the exclusion effect of LAB-SCS against H. pylori in AGS cells. The results showed that SCS from certain strains with higher concentrations of organic acids dramatically decreased the viability of H. pylori. We also proved that the organic acids could inhibit H. pylori adhesion and invasion of AGS cells. Furthermore, the concentration and speciation of organic acids in SCS after fermentation of LAB are important factors in the inhibition of H. pylori infection. In addition, the in vitro methods used in this study might provide for the rapid screening of potential probiotics with anti-H. pylori activity in the dairy industry.

Salivaricin CRL 1328 is a heat-stable bacteriocin produced by Lactobacillus salivarius CRL 1328, a strain isolated from healthy human vagina, with potential applications for preventing urogenital infections. The objective of this study was to characterize the locus responsible for salivaricin CRL 1328 production and its mechanism of action against Enterococcus faecalis MP97 as the sensitive strain. Oligonucleotides were designed based on sequences of antimicrobial peptides previously described in the literature. The salivaricin CRL 1328 cluster was identified, sequenced and analyzed. This cluster was similar to the previously described ABP118 which codified for a two-peptide bacteriocin. The putative mature peptides of salivaricin CRL 1328, Salalpha and Salbeta were chemically synthesized. These peptides did not show bacteriocin activity when assayed individually. Both peptides exhibited optimal antimicrobial activity at an equimolar ratio. Spectroscopic fluorescence assays were carried out using the synthetic peptides to study the effect of salivaricin on proton motive force. This bacteriocin was shown to dissipate membrane potential and the transmembrane proton gradient, both components of proton motive force. E. faecalis MP97 cells treated with salivaricin CRL 1328 peptides were observed in transmission electron microscopy which revealed ultrastructural modifications of the cell wall.

The aim of this study was to analyze the influence of vitamins, glycerol, and salts on the growth and bacteriocin production by Lactobacillus salivarius CRL 1328, a human vagina isolate, by using a chemically defined medium to determine the optimal conditions for salivaricin production. The single omission of <span class="smallcap">d</span>-biotin, thiamine, p-aminobenzoic acid, folic acid, or cyanocobalamin did not affect the bacterial growth, whereas the removal of nicotinic acid, riboflavin, and pyridoxal produced a decrease of about 30% in the growth rate. Maximum salivaricin activity was observed after the addition of 5 or 10 g/L of NaCl. On the basis of the nutritional requirements and the levels of salivaricin production, a new optimized and simplified defined medium (SDM-NaCl) for L. salivarius CRL 1328 bacteriocin production was formulated. The kinetics of salivaricin production in SDM-NaCl and in the complex media LAPTg revealed that bacteriocin production was growth linked. A combination of tricine - sodium dodecyl sulfate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE), Lumitein protein gel staining, and a bioassay for antibacterial activity indicated that the molecular mass of salivaricin CRL 1328 is about 4.5 kDa. The partially purified bacteriocin, obtained from SDM-NaCl after concentration, allowed for the design of a relatively simple method for the recovery of a biologically active protein.

Probiotics have a range of proposed health benefits for the consumer, which may include modulating the levels of beneficial elements in the microbiota. Recent investigations using molecular approaches have revealed a human intestinal microbiota comprising over 1000 phylotypes. Mechanisms whereby probiotics impact on the intestinal microbiota include competition for substrates, direct antagonism by inhibitory substances, competitive exclusion, and potentially host-mediated effects such as improved barrier function and altered immune response. We now have the microbial inventories and genetic blueprints to begin tackling intestinal microbial ecology at an unprecedented level of detail, aided by the understanding that dietary components may be utilized differentially by individual phylotypes. Controlled intervention studies in humans, utilizing latest molecular technologies, are required to consolidate evidence for bacterial species that impact on the microbiota. Mechanistic insights should be provided by metabolomics and other analytical techniques for small molecules. Rigorous characterization of interactions between the diet, microbiota, and probiotic bacteria will provide new opportunities for modulating the microbiota towards improving human health.

This review focuses on the structure and mode-of-action of non-lanthionine-containing peptide bacteriocins produced by Gram-positive bacteria. These bacteriocins may be divided into four groups:(i) the anti-listerial one-peptide pediocin-like bacteriocins that have very similar amino acid sequences,(ii) the two-peptide bacteriocins that consist of two different peptides,(iii) the cyclic bacteriocins, and (iv) the linear non-pediocin-like one-peptide bacteriocins. These bacteriocins are largely cationic, contain 20 to 70 residues, and kill cells through membrane-permeabilization. The pediocin-like bacteriocins are the ones that are best characterized. Upon contact with target membranes, their cationic N-terminal half forms a beta-sheet-like structure that binds to the target cell surface, while their more hydrophobic helical-containing C-terminal half penetrates into the hydrophobic core of target-cell membranes and apparently binds to the mannose phosphotransferase permease in a manner that results in membrane leakage. Immunity proteins that protect cells from being killed by pediocin-like bacteriocins bind to the bacteriocin-permease complex and prevent bacteriocin-induced membrane-leakage. Recent structural analyses of two-peptide bacteriocins indicate that they form a helix-helix structure that penetrates into cell membranes. Also these bacteriocins may act by binding to integrated membrane proteins. It is proposed that many membrane-active peptide bacteriocins kill target-cells through basically the same mechanism; the common theme being that a membrane-penetrating part of bacteriocins bind to a membrane embedded region of an integrated membrane protein, thereby causing conformational alterations in the protein that in turn lead to membrane-leakage and cell death.

Bacteria employed in probiotic applications help to maintain or restore a host's natural microbial floral. The ability of probiotic bacteria to successfully outcompete undesired species is often due to, or enhanced by, the production of potent antimicrobial toxins. The most commonly encountered of these are bacteriocins, a large and functionally diverse family of antimicrobials found in all major lineages of Bacteria. Recent studies reveal that these proteinaceous toxins play a critical role in mediating competitive dynamics between bacterial strains and closely related species. The potential use of bacteriocin-producing strains as probiotic and bioprotective agents has recently received increased attention. This review will report on recent efforts involving the use of such strains, with a particular focus on emerging probiotic therapies for humans, livestock, and aquaculture.

Relative predominance of each of five probiotic strains was investigated in the ileum of weaned pigs, compared with that in feces, when administered in combination at c. 5 x 10(9) CFU day(-1) for 28 days. Probiotic was excreted at 10(6)-10(9) CFU g(-1) feces, while ileal survival ranged from 10(2) to 10(6) CFU g(-1) digesta. In contrast to the feces, where Lactobacillus murinus DPC6002 predominated, the bacteriocin-producing Lactobacillus salivarus DPC6005 dominated over coadministered strains both in the ileum digesta and in mucosa. Probiotic administration did not alter counts of culturable fecal Lactobacillus or Enterobacteriaceae but higher ileal Enterobacteriaceae were observed in the ileal digesta of probiotic-fed pigs (P<0.05). We observed decreased CD25 induction on T cells and monocytes (P<0.01) and decreased CTLA-4 induction (P<0.05) by the mitogen phytohemagglutinin on CD4 T cells from the probiotic group. Probiotic treatment also increased the proportion of CD4+ CD8+ T cells within the peripheral T-cell population and increased ileal IL-8 mRNA expression (P<0.05). In conclusion, superior ileal survival of L. salivarius compared with the other coadministered probiotics may be due to a competitive advantage conferred by its bacteriocin. The findings also suggest that the five-strain combination may function as a probiotic, at least in part, via immunomodulation.

The aim of this study was to compare the impact of dietary supplementation with a Bifidobacterium breve strain together with linoleic acid & α-linolenic acid, for 7 weeks, on colonic sensitivity and fatty acid metabolism in rats. Maternally separated and non-maternally separated Sprague Dawley rats (n = 15) were orally gavaged with either B. breve DPC6330 (10(9) microorganisms/day) alone or in combination with 0.5%(w/w) linoleic acid & 0.5%(w/w) α-linolenic acid, daily for 7 weeks and compared with trehalose and bovine serum albumin. Tissue fatty acid composition was assessed by gas-liquid chromatography and visceral hypersensitivity was assessed by colorectal distension. Significant differences in the fatty acid profiles of the non-separated controls and maternally separated controls were observed for α-linolenic acid and arachidonic acid in the liver, oleic acid and eicosenoic acid (c11) in adipose tissue, and for palmitoleic acid and docosahexaenoic acid in serum (p<0.05). Administration of B. breve DPC6330 to MS rats significantly increased palmitoleic acid, arachidonic acid and docosahexaenoic acid in the liver, eicosenoic acid (c11) in adipose tissue and palmitoleic acid in the prefrontal cortex (p<0.05), whereas feeding B. breve DPC6330 to non separated rats significantly increased eicosapentaenoic acid and docosapentaenoic acid in serum (p<0.05) compared with the NS un-supplemented controls. Administration of B. breve DPC6330 in combination with linoleic acid and α-linolenic acid to maternally separated rats significantly increased docosapentaenoic acid in the serum (p<0.01) and α-linolenic acid in adipose tissue (p<0.001), whereas feeding B. breve DPC6330 with fatty acid supplementation to non-separated rats significantly increased liver and serum docosapentaenoic acid (p<0.05), and α-linolenic acid in adipose tissue (p<0.001). B. breve DPC6330 influenced host fatty acid metabolism. Administration of B. breve DPC6330 to maternally separated rats significantly modified the palmitoleic acid, arachidonic acid and docosahexaenoic acid contents in tissues. The effect was not observed in non-separated animals.

Alterations in intestinal microbiota composition are associated with several chronic conditions, including obesity and inflammatory diseases. The microbiota of older people displays greater inter-individual variation than that of younger adults. Here we show that the faecal microbiota composition from 178 elderly subjects formed groups, correlating with residence location in the community, day-hospital, rehabilitation or in long-term residential care. However, clustering of subjects by diet separated them by the same residence location and microbiota groupings. The separation of microbiota composition significantly correlated with measures of frailty, co-morbidity, nutritional status, markers of inflammation and with metabolites in faecal water. The individual microbiota of people in long-stay care was significantly less diverse than that of community dwellers. Loss of community-associated microbiota correlated with increased frailty. Collectively, the data support a relationship between diet, microbiota and health status, and indicate a role for diet-driven microbiota alterations in varying rates of health decline upon ageing.

Cronobacter species are opportunistic pathogens, and a mortality rate of 40 to 80% is associated with infections. This pathogen can cause a range of serious diseases such as meningitis, septicemia, necrotizing enterocolitis, and brain abscesses and has been responsible for a variety of sequelae such as quadriplegia. Although Cronobacter can cause disease in both adults and infants, infant infections associated with powdered formula are the focus of this review. Since the first reported Cronobacter infection outbreak in 1958, powdered infant formula has been identified as a major source of these outbreaks, resulting in many recalls of powdered infant formula worldwide. This contamination has created an immense problem for the powdered infant formula industry. In this review, we discuss the taxonomy of Cronobacter species, the natural habitat of Cronobacter and its presence in foods, the physiology, pathogenicity, and virulence of Cronobacter species, and available detection methods. We also discuss reported cases of Cronobacter infection linked to powdered infant formula consumption and then focus specifically on the official World Health Organization guidelines for preparation of powdered infant formula.

Caseicins A and B are low-molecular-weight antimicrobial peptides which are released by proteolytic digestion of sodium caseinate. Caseicin A (IKHQGLPQE) is a nine-amino-acid cationic peptide, and caseicin B (VLNENLLR) is a neutral eight-amino-acid peptide; both have previously been shown to exhibit antibacterial activity against a number of pathogens, including Cronobacter sakazakii. Previously, four variants of each caseicin which differed subtly from their natural counterparts were generated by peptide synthesis. Antimicrobial activity assays revealed that the importance of a number of the residues within the peptides was dependent on the strain being targeted. In this study, this engineering-based approach was expanded through the creation of a larger collection of 26 peptides which are altered in a variety of ways. The investigation highlights the generally greater tolerance of caseicin B to change, the fact that changes have a more detrimental impact on anti-Gram-negative activity, and the surprising number of variants which exhibit enhanced activity against Staphylococcus aureus.

The draft genome of Bifidobacterium breve DPC 6330, isolated from an elderly patient, was determined. B. breve DPC 6330 was previously identified to synthesize the beneficial metabolite conjugated linoleic acid from free linoleic acid. The sequence will allow identification and characterization of the genetic determinants of its putative beneficial properties.

Genetic diversity and genomic rearrangements are a driving force in bacterial evolution and niche adaptation. We sequenced and annotated the genome of Lactobacillus johnsonii DPC6026, a strain isolated from the porcine intestinal tract. Although the genome of DPC6026 is similar in size (1.97 mbp) and GC content (34.8%) to the sequenced human isolate L. johnsonii NCC 533, a large symmetrical inversion of approximately 750 kb differentiated the two strains. Comparative analysis among 12 other strains of L. johnsonii including 8 porcine, 3 human and 1 poultry isolate indicated that the genome architecture found in DPC6026 is more common within the species than that of NCC 533. Furthermore a number of unique features were annotated in DPC6026, some of which are likely to have been acquired by horizontal gene transfer (HGT) and contribute to protection against phage infection. A putative type III restriction-modification system was identified, as were novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) elements. Interestingly, these particular elements are not widely distributed among L. johnsonii strains. Taken together these data suggest intra-species genomic rearrangements and significant genetic diversity within the L. johnsonii species and indicate towards a host-specific divergence of L. johnsonii strains with respect to genome inversion and phage exposure.

Caseicin A (IKHQGLPQE) and caseicin B (VLNENLLR) are antimicrobial peptides generated through the bacterial fermentation of sodium caseinate, and on the basis of this and previous studies, they are active against many Gram-negative pathogens (Cronobacter sakazakii, Cronobacter muytjensii, Salmonella enterica serovar Typhimurium, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas fluorescens) as well as the Gram-positive organism Staphylococcus aureus. Here we describe further studies with the aim of establishing the importance of specific (charged and nonpolar aliphatic) residues within the caseicin peptides and the effects that they have on the bacteria listed above. In order to achieve our objective, we created four derivatives of each caseicin (A1 to A4 and B1 to B4) in which specific residues were altered, and results obtained with these derivatives were compared to wild-type caseicin activity. Although conversion of cationic residues to alanine in caseicins B1 (R8A change), A1 (K2A), A2 (H3A), and A3 (K2A-H3A) generally resulted in their activity against microbial targets being reduced or unaltered, C. sakazakii DPC6440 was unusual in that it displayed enhanced sensitivity to three peptides (caseicins A1, A3, and B2) in which positively charged residues had been eliminated. While the replacement of leucine with alanine in selected variants (B3 and B4) resulted in reduced activity against a number of strains of Cronobacter and, in some cases, S. Typhimurium, these changes enhanced the activities of these peptides against DPC6440 and a number of S. aureus strains. It is thus apparent that the importance of specific residues within the caseicin peptides is dependent on the strain being targeted.

A variety of milk-derived biologically active peptides have been shown to exert both functional and physiological roles in vitro and in vivo, and because of this are of particular interest for food science and nutrition applications. Biological activities associated with such peptides include immunomodulatory, antibacterial, anti-hypertensive and opioid-like properties. Milk proteins are recognized as a primary source of bioactive peptides, which can be encrypted within the amino acid sequence of dairy proteins, requiring proteolysis for release and activation. Fermentation of milk proteins using the proteolytic systems of lactic acid bacteria is an attractive approach for generation of functional foods enriched in bioactive peptides given the low cost and positive nutritional image associated with fermented milk drinks and yoghurt. In Part II of this review, we focus on examples of milk-derived bioactive peptides and their associated health benefits, to illustrate the potential of this area for the design and improvement of future functional foods.

A variety of milk-derived biologically active peptides have been shown to exert both functional and physiological roles in vitro and in vivo, and because of this are of particular interest for food science and nutrition applications. Biological activities associated with such peptides include immunomodulatory, antibacterial, anti-hypertensive and opioid-like properties. Milk proteins are recognized as a primary source of bioactive peptides, which can be encrypted within the amino acid sequence of dairy proteins, requiring proteolysis for release and activation. Fermentation of milk proteins using the proteolytic systems of lactic acid bacteria (LAB) is an attractive approach for generation of functional foods enriched in bioactive peptides given the low cost and positive nutritional image associated with fermented milk drinks and yoghurt. In this review, we discuss the exploitation of such fermentation towards the development of functional foods conferring specific health benefits to the consumer beyond basic nutrition. In particular, in Part I, we focus on the release of encrypted bioactive peptides from a range of food protein sources, as well as the use of LAB as cell factories for the de novo generation of bioactivities.

Salmonella spp. infection is a major cause of gastroenteritis, with many thousands of cases reported in the European Union every year. The use of probiotics offers the potential to improve this situation. Here, we investigate the effects of oral treatment of pigs with a defined lactic acid bacteria culture mixture on both clinical and microbiological signs of Salmonella enterica serovar Typhimurium infection. Fifteen weaned pigs blocked by sex and weight were administered control milk or a mixture of five probiotic strains as either a milk fermentate or milk suspension for a total of 30 days. The mixture consisted of two strains of Lactobacillus murinus and one strain each of Lactobacillus salivarius subsp. salivarius, Lactobacillus pentosus, and Pediococcus pentosaceous. Following probiotic administration for 6 days, animals were challenged orally with serovar Typhimurium; the health of the animals and the microbiological composition of their feces were monitored for 23 days postinfection. Animals treated with probiotic showed reduced incidence, severity, and duration of diarrhea. These animals also gained weight at a greater rate than control pigs administered skim milk. Mean fecal numbers of Salmonella were significantly reduced in probiotic-treated animals at 15 days postinfection (P = 0.01). The administered probiotic bacteria improved both the clinical and microbiological outcome of Salmonella infection. These strains offer significant benefit for use in the food industry and may have potential in human applications.

Six Tahitian liverworts, Trichocolea pluma, Chandonanthus hirtellus, Mastigophora diclados, Jungermannia sp., Plagiochila sp. and Cyathodium foetidissimum were chemically investigated. All of these liverworts produce their own characteristic compounds. Vanillic acid methyl ester was isolated for the first time from T. pluma. Skatol is responsible for the very intense unpleasant odor of C. foetidissimum. Herbertane-type sesquiterpenoids are peculiar components of M. diclados, and fusicoccane-type diterpenoids were identified in Pagiochila sp. Cembranes and ent-verticillanes were isolated from C. hirtellus and also detected in Jungermannia species. C. hirtellus also biosynthesizes algal components and such results may suggest that some liverworts originate from algae.

Asaia lannaensis sp. nov. was described for two strains isolated from flowers of the spider lily collected in Chiang Mai, Thailand. The isolates produced acetic acid from ethanol on ethanol/calcium carbonate agar, differing from the type strains of Asaia bogorensis, Asaia siamensis, and Asaia krungthepensis, but did not grow in the presence of 0.35% acetic acid (v/v). The new species is the fourth of the genus Asaia, the family Acetobacteraceae.

We selected in vitro erythromycin-resistant strains of Bartonella henselae. The mutants obtained had point mutations in domain V of 23S rRNA and/or in ribosomal protein L4. One lymph node of a patient with cat-scratch disease had such a mutation in 23S rRNA, suggesting that natural resistant strains may infect humans.

A narrow-spectrum clavulanic acid-inhibited class A beta-lactamase, BOR-1, was identified in a Bordetella bronchiseptica clinical isolate. It shared 45% amino acid identity with L-2 from Stenotrophomonas maltophilia. An identical beta-lactamase gene was found in B. bronchiseptica and Bordetella parapertussis reference strains that may contribute only in part to their resistance phenotype.

An homology model of human adenylosuccinate lyase structure shows that P100A substitution distorts the amino acid chain of domain I in the proximity of His-86, which behaves as general acid in the catalysis, and may expose Cys-98 and Cys-99 to oxidising agents. This model is in line with the observation that the defective protein is strongly inhibited by 4-hydroxy-2-nonenal, an hydroxyalkenal that is known to form thio-ether linkage with proteins.

We have demonstrated that the bldB gene of Streptomyces coelicolor is required for the formation of aerial hyphae and the synthesis of antibiotics. We also found that BldB forms a higher-order complex (most likely a dimer) and that amino acid residues 20 to 78 are important for this interaction. This region is conserved in the BldB family, suggesting that dimer formation may be a common feature of these proteins.

Pseudomonas aeruginosa clinical isolate PA35 is resistant to amino- and ureido-penicillins, has intermediate susceptibility to cefsulodin, cefepime and aztreonam, and is susceptible to imipenem and ceftazidime. Cloning and sequencing revealed a new beta-lactamase variant, OXA-35, sharing 96% amino acid identity with OXA-10. OXA-35 displays a restricted-substrate hydrolysis profile with improved hydrolysis of amoxicillin and cloxacillin compared with OXA-10. OXA-35 differs from derivatives OXA-19 and OXA-28 by one amino acid substitution and may be a progenitor of these OXA-13-like extended-spectrum beta-lactamases.

Recent studies have shown that mutations in two amino acid positions of the Pneumocystis carinii dihydropteroate synthase gene are significantly more common in immunocompromised patients with P. carinii pneumonia who fail sulfa or sulfone prophylaxis. This paper reviews the studies that suggest that these mutations may be responsible for some failures of prophylaxis in P. carinii.

Analysis of a G-protein coupled receptor fragment isolated from the leech CNS reveals that it is a chimeric cannabinoid/melanocortin receptor. Two regions of the leech sequence display high levels of amino acid identity with mammalian cannabinoid receptors while a third region is 98% identical to part of the bovine adrenocorticotropic hormone receptor. The leech receptor may therefore resemble the putative ancestor of mammalian cannabinoid and melanocortin receptors.

Analysis of a G-protein coupled receptor fragment isolated from the leech CNS reveals that it is a chimeric cannabinoid/melanocortin receptor. Two regions of the leech sequence display high levels of amino acid identity with mammalian cannabinoid receptors while a third region is 98% identical to part of the bovine adrenocorticotropic hormone receptor. The leech receptor may therefore resemble the putative ancestor of mammalian cannabinoid and melanocortin receptors.