Antibiotic resistance and pathogenicity factors in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> isolated from mastitic Sahiwal cattle

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious problem in dairy animals suffering from mastitis. In the present study, the distribution of mastitic MRSA and antibiotic resistance was studied in 107 strains of S. aureus isolated from milk samples from 195 infected udders. The characterizations pathogenic factors (adhesin and toxin genes) and antibiotic susceptibility of isolates were carried out using gene amplification and disc diffusion assays, respectively. A high prevalence of MRSA was observed in the tested isolates (13.1%). The isolates were also highly resistant to antibiotics, i.e. 36.4% were resistant to streptomycin, 33.6% to oxytetracycline, 29.9% to gentamicin and 26.2% each to chloramphenicol, pristinomycin and ciprofloxacin. A significant variation in the expression of pathogenic factors (Ig, coa and clf) was observed in these isolates. The overall distribution of adhesin genes ebp, fib, bbp, fnbB, cap5, cap8, map and cna in the isolates was found to be 69.1, 67.2, 6.5, 20.5, 60.7, 26.1, 81.3 and 8.4%, respectively. The presence of fib, fnbB, bbp and map genes was considerably greater in MRSA than in methicillin-susceptible S. aureus (MSSA) isolates. The proportions of toxin genes, namely, hlb, seb, sec, sed, seg and sei, in the isolates were found to be 94.3, 0.9, 8.4, 0.9, 10.2 and 49.5%, respectively. The proportions of agr genes I, II, III and IV were found to be 39.2, 27.1, 21.5 and 12.1%, respectively. A few isolates showed similar antibiotic-resistance patterns, which could be due to identical strains or the dissemination of the same strains among animals. These findings can be utilized in mastitis treatment programmes and antimicrobials strategies in organized herds.     

Allometry between leg and body length of insects: lack of support for the size–grain hypothesis

• 1 The size–grain hypothesis ( Kaspari & Weiser, 1999 ) states that (1) as organisms decrease in size, they perceive their environment as being more rugose; (2) long legs allow organisms to step over obstacles but hinder them from entering small gaps; and (3) as the size of an organism decreases, the benefits of long legs begin to be outweighed by the costs of construction. Natural selection should therefore favour proportionally longer legs in larger organisms, thereby leading to a positive allometry between leg and body length (scaling exponent b > 1).
• 2 Here we compare the scaling exponent of leg‐to‐body length relationships among insects that walk, walk and fly, and predominantly fly. We measured the lengths of the hind tibia, hind femur, and body length of each species.
• 3 The taxa varied considerably in the scaling exponent b. In seven out of ten groups (Formicidae, Isoptera, Carabidae, Pentatomidae, Apidae, Lepidoptera, Odonata adult), b was significantly greater than one. However, there was no gradual decrease in b from walking to walking/flying to flying insects.
• 4 The results of the present study provide no support for the size–grain hypothesis. We propose that leg length is not only affected by the rugosity of the environment, but also by (1) functional adaptations, (2) phylogeny, (3) lifestyle, (4) the type of insect development (hemimetabolism or holometabolism), and (5) constraints of gas exchange.

     

GRIESBACHIAN AND DIENERIAN (EARLY TRIASSIC) AMMONOID FAUNAS FROM NORTHWESTERN GUANGXI AND SOUTHERN GUIZHOU (SOUTH CHINA)

Abstract: Intensive sampling of the Luolou (northwestern Guangxi) and the Daye (southern Guizhou) Formations in South China leads to the recognition of a regional Griesbachian and Dienerian ammonoid succession for this key palaeobiogeographical area. The new biostratigraphical sequence comprises the upper Griesbachian ‘Ophiceras beds’ and the lower Dienerian ‘Proptychites candidus beds’, which are separated from the uppermost Dienerian ‘Clypites beds’ by an unfossiliferous interval. These faunas contain some taxa with wide geographic distribution (e.g. Ambites, Pleurambites, Pleurogyronites, Proptychites candidus), thus facilitating correlation with faunal successions from other regions (i.e. British Columbia, Canadian Arctic, Himalayas and South Primorye). Two new genera (Jieshaniceras and Shangganites) and three new species (Anotoceras subtabulatus, Pleurambites radiatus and Shangganites shangganense) are described.     

Patterns of cervical metastasis from carcinoma of the oral tongue

Background  

Cancer of the oral tongue is the second most common cancer among males in various parts of India. Despite advances in diagnosis and treatment the failure rates in cancer of the oral tongue are high and survival poor. Majority of these failures occur in untreated neck.     

Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1

Background  

The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK), encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions.     

A faster migrating variant masquerades as NICD when performing in vitro gamma-secretase assays with bacterially expressed Notch substrates

Intramembrane proteolysis is a new and rapidly growing field. In vitro assays utilizing recombinant substrates for gamma-secretase, an intramembrane-cleaving enzyme, are critically important in order to characterize the biochemical properties of this unusual enzyme. Several recombinant Notch proteins of varying length are commonly used as in vitro substrates for CHAPSO-solubilized gamma-secretase. Here we report that several recombinant Notch constructs undergo limited or no proteolysis in vitro. Instead, upon incubation with or without gamma-secretase, variants of the intact protein migrate during SDS-PAGE at the location expected for the gamma-secretase specific cleavage products. In addition, we show that addition of aspartyl- and gamma-secretase specific protease inhibitors are able to retard the formation of these variants independent of gamma-secretase, which could lead to the erroneous conclusion that Notch cleavage by solubilized gamma-secretase was achieved in vitro even when no proteolysis occurred. In contrast, substrates produced in mammalian or insect cells are cleaved efficiently in vitro. These observations suggest that in vitro studies reliant on recombinant, bacterially produced Notch TMD should be performed with the inclusion of additional controls able to differentiate between actual cleavage and this potential artifact.     

PepN,the major Suc-LLVY-AMC-hydrolyzing enzyme in Escherichia coli,displays functional similarity with downstream processing enzymes in Archaea and eukarya. Implications in cytosolic protein degradation

Succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin (Suc-LLVY-AMC), a fluorogenic endopeptidase substrate, is used to detect 20 S proteasomal activity from Archaea to mammals. An o-phenanthroline-sensitive Suc-LLVY-AMC hydrolyzing activity was detected in Escherichia coli although it lacks 20 S proteasomes. We identified PepN, previously characterized as the sole alanine aminopeptidase in E. coli, to be responsible for the hydrolysis of Suc-LLVY-AMC. PepN is an aminoendopeptidase. First, extracts from an ethyl methanesulfonate-derived PepN mutant, 9218, did not cleave Suc-LLVY-AMC and L-Ala-para-nitroanilide (pNA). Second, biochemically purified PepN cleaves a wide variety of both aminopeptidase and endopeptidase substrates, and L-Ala-pNA is cleaved more efficiently than other substrates. Studies with bestatin, an aminopeptidase-specific inhibitor, suggest differences in the mechanisms of cleavage of aminopeptidase and endopeptidase substrates. Third, PepN hydrolyzes whole proteins, casein and albumin. Finally, an E. coli strain with a targeted deletion in PepN also lacks the ability to cleave Suc-LLVY-AMC and L-Ala-pNA, and expression of wild type PepN in this mutant rescues both activities. In addition, we identified a low molecular weight Suc-LLVY-AMC-cleaving peptidase in Mycobacterium smegmatis, a eubacteria harboring 20 S proteasomes, to be an aminopeptidase homologous to E. coli PepN, by mass spectrometry analysis. "Sequence-based homologues" of PepN include well characterized aminopeptidases, e.g. Tricorn interacting factors F2 and F3 in Archaea and puromycin-sensitive aminopeptidase in mammals. However, our results suggest that eubacterial PepN and its homologues displaying aminoendopeptidase activities may be "functionally similar" to enzymes important in downstream processing of proteins in the cytosol: Tricorn-F1-F2-F3 complex in Archaea and TPPII/Multicorn in eukaryotes.