Abstract: This invention provides a novel compound of the formula: ##STR1## wherein X is L-HyPro or L-Pro, R is --CH.sub.3 or --CH(CH.sub.3).sub.2, and n is an integer from 9 to 12, or its salt, a process for producing the compound which comprises cultivating a microorganism which belongs to the genus Pseudomonas and produces the compound in a medium and recovering the compound from the medium and a biologically pure culture of Pseudomas sp. PB-6250 producing the compound.

Abstract: A compound of the formula (I): ##STR1## wherein R is: (CH.sub.2).sub.8 CH.sub.3,(CH.sub.2).sub.3 CH.sup.(cis) CH(CH.sub.2).sub.5 CH.sub.3,(CH.sub.2).sub.10 CH.sub.3, or(CH.sub.2).sub.4 CH.sup.(cis) CH(CH.sub.2).sub.6 CH.sub.3.or salt thereof, and a microorganism producing the compound are provided.

Abstract: An anti-mycoplasma agent comprising tropolone, its derivatives, represented by the formula: ##STR1## (wherein R.sub.1 is hydroxy, aliphatic acyloxy, arylacyloxy, arysulfonyloxy, carboxyalkyloxy or its ester, benzoylalkyloxy, alkenyloxy, 1,3-dihydro-3-oxo-1-isobenzofuranyloxy, (2-oxo-5-methyl-1,3-dioxol-4-yl)methyloxy or thiocyanato and R.sub.2 is hydrogen, halogen, hydroxy, alkyl or alkoxy) and their salts as an active ingredient, which has potent activity especially against tylosin-resistant mycoplasma both in vitro and in vivo and is effectively used in treating the diseases caused thereby.

Abstract: A new antibiotic having .beta.-lactamase inhibitory activity, PA-31088-IV, being useful as a medicament and a veterinary drug for inhibiting the growth of gram-positive and gram-negative phathogenic microorganisms and a process for preparing the same, being characterized by cultivating Streptomyces tokunonensis sp. nov. in a suitable medium and recovering PA-31088-IV from the cultured broth.