Identification and topographical characterisation of microbial nanowires in Nostoc punctiforme

Abstract

Extracellular pili-like structures (PLS) produced by cyanobacteria have been poorly explored. We have done detailed topographical and electrical characterisation of PLS in Nostoc punctiforme PCC 73120 using transmission electron microscopy (TEM) and conductive atomic force microscopy (CAFM). TEM analysis showed that N. punctiforme produces two separate types of PLS differing in their length and diameter. The first type of PLS are 6-7.5 nm in diameter and 0.5-2 µm in length (short/thin PLS) while the second type of PLS are ~20-40 nm in diameter and more than 10 µm long (long/thick PLS). This is the first study to report long/thick PLS in N. punctiforme. Electrical characterisation of these two different PLS by CAFM showed that both are electrically conductive and can act as microbial nanowires. This is the first report to show two distinct PLS and also identifies microbial nanowires in N. punctiforme. This study paves the way for more detailed investigation of N. punctiforme nanowires and their potential role in cell physiology and symbiosis with plants.

Iron and phosphorus deprivation induce sociality in the marine bloom-forming cyanobacterium Trichodesmium

“…Additionally, the hair-like structures we observed extruding from the trichomes (Fig. 2f) may be similar to pili-like structures as discovered in several cyanobacteria [44], including the filamentous Nostoc punctiforme that has two types of pili-like structures, short/thin pili-like structures as in other bacteria, and novel interconnecting long/ thick pili-like structures [45]. Both types of pili-like structures can act as microbial nanowires, however their function remains unknown [45].…”

Microbial nanowires: an electrifying tale

“…Thus, Mi. aeruginosa and Nostoc punctiforme might be producing MNWs, which has been confirmed by conductive atomic force microscopy (AFM) analysis (Sure et al, 2015(Sure et al, , 2016b. The discovery of MNWs in such diverse micro-organisms ranging from anaerobic, metalreducing bacteria to photosynthetic, aerobic cyanobacteria strengthens the viewpoint that they may be pervasive in the environment.…”

“…Two distinct types of MNWs (first, short/thin MNWs of size 6-7.5 nm in diameter and 0.5-2 µm in length and second, long/thick MNWs of size~20-40 nm in diameter and !10 µm long) were observed in No. punctiforme (Sure et al, 2016b). The identity of MNWs from multispecies biofilms observed in BRONJ could also not be confirmed .…”

“…This long-range electron transfer thus has been shown to increase electricity production by 10 times (Reguera et al, 2006). Along the same lines, MNWproducing photosynthetic micro-organisms (Gorby et al, 2006;Sure et al, 2015;2016b) may be helpful in improving the efficiency of photosynthetic microbial fuel cells and microbial solar cells (Rosenbaum et al, 2010;Strik et al, 2011).…”

“…hydrophila, R. palustris, D. desulfuricans and No. punctiforme but their identity has not been confirmed so far Eaktasang et al, 2016;Sure et al, 2016b;Venkidusamy et al, 2015). Two distinct types of MNWs (first, short/thin MNWs of size 6-7.5 nm in diameter and 0.5-2 µm in length and second, long/thick MNWs of size~20-40 nm in diameter and !10 µm long) were observed in No.…”