No abstract

In prokaryotes, only a few examples of differential gene expression in cell populations have been described. Colicin production in natural populations of Escherichia coli, while providing a competitive advantage in the natural habitat, also leads to lysis of the toxin-producing cell. Colicin K synthesis has been found to be induced due to an increase in ppGpp (I. Kuhar, J. P. van Putten, D. Žgur-Bertok, W. Gaastra, and B. J. Jordi, Mol. Microbiol. 41:207-216). Using two transcriptional fusions, cka-gfp and cki-gfp, we show that at the single-cell level, the colicin K activity gene cka is expressed in only 3% of the bacterial population upon induction by nutrient starvation. In contrast, the immunity gene cki is expressed in the large majority of the cells. Expression of the cka-gfp fusion in a lexA-defective strain and in a relA spoT mutant strain indicates that differential expression of cka is established primarily at the level of transcription.

IzvlečekUDK 579.2:551.44 Mikroorganizmi podzemlja: primeri iz slovenskih kraških jam Mikroorganizmi v jama� naseljujejo različne �abitate, kjer razvijejo številne interakcije. Kot dokaz mikrobne aktivnosti la�ko naletimo na številne biološko pogojene kraške oblike. Mikroorganizmi so vklučeni tako v litogene kot litolitične procese. Poleg �eterotrofni� organizmov la�ko v jama� pričakujemo tudi avtotrofne. Nekatere cianobakterije in mikroalge la�ko preživijo v jama� tudi pri tisti� intenziteta� svetlobe, ki so nižje od nji�ove fotosintetske kompenzacijske točke. V prispevku so predstavljena na�ajališča in mikroorganizmi (bakterije, cianobakterije, mikroalge, glive in praživali), ki so bili do sedaj identificirani v slovenski� jama�. Posebej bakterije, kot najbolj raznovrstna skupina mikroorganizmov, ponujajo ogromen biote�nološki in bioremediacijski potencial. Mikrobna biomasa predstavlja v jama� upoštevanja vreden vir �rane za višje razvite jamske organizme. Jame v Sloveniji predstavljajo še veliko možnosti za odkritje novi� vrst, kot je primer glive mucor troglophilus, ki je bila odkrita na jamski kobilici Troglophilus neglectus. Ključne besede: mikroorganizmi, jamska mikrobiologija, kras, Slovenija. In caves microorganisms in�abit distinct �abitats w�ere t�ey develop various interactions. As an evidence of microbial activity several features can be identified. Microorganisms are involved bot� in lit�ogenic and lit�olitic processes. Besides �et-erotrop�s in caves autotrop�ic organisms can be also expected. Some cyanobacteria and microalgae in caves can survive even at p�oton flux densities lower t�an t�eir p�otosynt�etic compensation point. In t�e paper up-to-date identified groups of microorganisms (bacteria, cyanobacteria, microalgae, fungi and protozoa) wit� t�eir localities in Slovenian caves are presented. Especially bacteria from caves, as t�e most diverse group, offer immense biotec�nological and bioremediation potential. In caves microbial biomass can be considered a considerable food source for cave-dwelling �ig�er organisms. Caves in Slovenia offer great c�ances to discover new species, as was fungus mucor troglophilus discovered in association wit� t�e cave cricket Troglophilus neglectus.

Bioaerosols in cave air can serve as natural tracers and, together with physical parameters, give a detailed view of conditions in the cave atmosphere and responses to climatic changes. Airborne microbes in the Postojna Cave system indicated very dynamic atmospheric conditions, especially in the transitory seasonal periods between winter and summer. Physical parameters of cave atmosphere explained the highest variance in structure of microbial community in the winter and in the summer. The airborne microbial community is composed of different microbial groups with generally low abundances. At sites with elevated organic input, occasional high concentrations of bacteria and fungi can be expected of up to 1,000 colony-forming units/m(3) per individual group. The most abundant group of airborne amoebozoans were the mycetozoans. Along with movements of air masses, airborne algae also travel deep underground. In a cave passage with elevated radon concentration (up to 60 kBq/m(3)) airborne biota were less abundant; however, the concentration of DNA in the air was comparable to that in other parts of the cave. Due to seasonal natural air inflow, high concentrations of biological and inanimate particles are introduced underground. Sedimentation of airborne allochthonous material might represent an important and continuous source of organic material for cave fauna.

Oana T. Moldovan, Tanja Pipan, Sanda Iepure, Andrej Mi hevc & Janez Mulec: Biodiversity and ecology of fauna in per colating water in selected Slovenian and Romanian cavesBiodiversity and ecology of fauna in percolating water from Slovenian and Romanian caves was studied. Researc� focused on unravelling t�e community structure of epikarst fauna, w�ic� is carried away by t�e trickles of percolating water from t�e epikarst and vadose zones. The major part of t�e fauna found in percolating water is represented by copepods. This fauna, originating in t�e epikarst, was analysed and by means of t�e systematic sampling and observation t�e same groups of animals were found in Slovenian and Romanian caves. Differences among caves and sampling points indicate t�at epikarst is a �eterogenous �abitat. Relations�ip between faunal ric�ness and t�e p�ysical c�aracteristics of t�e water was found. Correlation between surface geomorp�ology and fauna in percolating water was statistically significant in t�e Postojna cave system. IzvlečekUDK 574.5:551.44(497.4+498) Oana T. Moldovan, Tanja Pipan, Sanda Iepure, Andrej Mi hevc & Janez Mulec: Biodiverziteta in ekologija favne v pre nikli vodi izbranih slovenskih in romunskih jamV prenikli vodi iz slovenski� in romunski� jam smo proučevali biodiverziteto in ekologijo favne. V raziskavi smo se osredotočili na proučevanje združbe epikraške favne, ki jo odnašajo curki prenikle vode iz epikraške in nezasičene cone. Največji delež organizmov v prenikli vodi zavzemajo ceponožni raki. Na podlagi sistematičnega vzorčenja in opravljeni� analiz smo v jama� slovenskega in romunskega krasa ugotovili prisotnost enaki� skupin organizmov. Razlike med jamami in posameznimi vzorčnimi mesti nakazujejo, da je epikras �eterogeni �abitat. Ugotovili smo statistično značilno povezavo med prisotnostjo določeni� skupin organizmov in fizikalnimi parametri vode. Korelacija med površinsko geomorfologijo Postojnskega jamskega sistema in številom ceponožni� rakov v prenikli vodi je bila statistično značilna.